Keto tuna casserole

Keto tuna casserole

Just like mom used to make—NOT. Ditch the noodles in favor of celery, onions, and peppers, and indulge in a keto meal that's ready in 30 minutes. It's a whole new, delicious thing.

Keto tuna casserole

Just like mom used to make—NOT. Ditch the noodles in favor of celery, onions, and peppers, and indulge in a keto meal that's ready in 30 minutes. It's a whole new, delicious thing.
USMetric
4 servingservings

Ingredients

  • 2 oz. 55 g butter
  • 1 (4 oz.) 1 (110 g) yellow onionyellow onions
  • 1 (5 oz.) 1 (140 g) green bell peppergreen bell peppers
  • 5½ oz. (1½ cups) 160 g (375 ml) celery stalkcelery stalks
  • 1 lb 450 g tuna in olive oil, drained
  • 1 cup 240 ml mayonnaise
  • 1 cup (2¾ oz.) 240 ml (80 g) shredded Parmesan cheese
  • 1 tsp 1 tsp chili flakes
  • salt and pepper
Serving
  • 6 oz. (523 cups) 170 g (1.3 liters) baby spinach
  • ¼ cup 60 ml olive oil
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Instructions

Instructions are for 4 servings. Please modify as needed.

  1. Preheat the oven to 400°F (200°C). Chop onion, bell pepper and celery finely and fry in butter in a large frying pan until slightly soft. Season with salt and pepper.
  2. Mix tuna, mayonnaise, parmesan cheese and chili flakes in a greased baking dish. Add fried vegetables and stir.
  3. Bake for 15-20 minutes or until golden brown.
  4. Serve with baby spinach and olive oil.

Tip!

Canned tuna is a life-saver when fridge and freezer are empty. Try to choose high-quality, MSC-labeled tunafish—preferably in olive oil instead of sunflower oil.

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A little sneak peek...

With Diet Doctor Plus you get access to tons of keto meal plans, including dairy-free and vegetarian versions, meal plans adapted for intermittent fasting, quick-and-easy and budget keto meal plans. Below, see our latest one.

Keto: Enjoy losing weight (16:8) #1

If you want to lose weight while still enjoying amazing food, we’ve got the perfect meal plan for you.

To help turn you into a fat-burning machine, we’ve decided to employ intermittent fasting (16:8) in this week’s meal plan. This means your first meal will be at lunch — but feel free to drink coffee, tea, and of course, water throughout the day.

This mouth-watering ketogenic menu will keep you way below 20 grams of carbs per day. It includes some popular budget-friendly meals, such as our No-bean keto chili and Crispy tuna burgers, plus a few more elevated meals like our
Ribeye steak with loaded cauliflower mash.

Remember, you can always swap pricey ingredients such as ribeye with cheaper protein options such as chicken thighs or pork chops. Just make sure to adjust the cooking time as needed.

By skipping breakfast, you’ll automatically save money that you could potentially spend on higher-quality ingredients such as grass-fed beef and organic eggs — a good investment for your body, the animals, and the environment.

Full meal plan →

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76 comments

  1. Kristin Parker Team Diet Doctor

    Can I freeze

    Yes, you can freeze this dish.

  2. Venencia
    i made this last night and used ingredients as specified. didn't measure the mayo, just eyeballed and the dish came out very nice and not too much oil. used Monterrey jack cheese. perfect dish. my 18 months daughter loved it very much.
  3. Karyn
    I've made this a lot as it is really quick and very tasty. I use tuna in brine as all the options I can find in olive oil are a dodgy sounding "blend". I also add some konjac noodles to bulk it up a bit.
  4. Venencia
    this time i used tuna in brine and feta cheese- delicious and not oily
  5. Sam
    What is best to substitute for the celery? I cant stand celery 🤮
    Replies: #56, #59
  6. Kristin Parker Team Diet Doctor

    What is best to substitute for the celery? I cant stand celery 🤮

    You may wish to omit the celery, there is not a great substitute.

  7. Deborah Murphy
    This was sooooo good! 5 stars 🌟

    I used my cast iron skillet so sautéed the vegetables and then added the rest and popped in oven. One pan clean up made it that much better.

  8. Zoe
    Made a batch of this today! Delicious flavours but too oily for my taste. Had to drain the oil off before eating. I will definitely try it next with sour cream and philly instead of the mayo. Oh... I also added some lemon juice and chopped fresh chives. Super tasty!
  9. Leigh Batten
    I swapped the celery for chopped pickled cucumbers (Mrs Elswoods if you're in the UK) gave a nice crunch and slightly sour against the salty tuna and cheese, delicious!
  10. Kathleen
    I made this and used cream of mushroom and added green beans. At the end I broiled it a bit. Has anyone ate this cold? Or would you suggest always heating it up? I ate some fresh out of the oven and served on spinach. It was lovely and filling, comfort food for sure!!
    Reply: #63
  11. Bonnie
    What are the carbs, protein, calories, and portion size to this dish? Thank you 😊
    Reply: #62
  12. Kristin Parker Team Diet Doctor

    What are the carbs, protein, calories, and portion size to this dish? Thank you 😊

    This dish makes four servings as written. All of the nutrition information is in the Nutrition+ tab under the list of ingredients.

  13. alexiaday
    Wouldn't the cream of mushroom add carbs to it? Or was it homemade?
  14. Wendy
    We absolutely love this dish! The freshly Parmesan makes such a difference. The only addition I make is green olives. Thanks DD
  15. Tori
    This was delicious but way too oily for me. Definitely won't put oil on the spinach as well but I'm keen to try tweaking it a little as it was so great to be eating tuna, which we love in this house!
  16. Tori
    This time I made it with sour cream, not mayo and also put lemon juice over it before serving and it was really good. I also didn't dress the baby spinach with olive oil and it was a whole new dish!
  17. Natalie
    what is considered one a serving size for this, 1 cup, 1/2 cup? This is not in the nutritional value Thank you
    Reply: #68
  18. Kristin Parker Team Diet Doctor

    what is considered one a serving size for this, 1 cup, 1/2 cup? This is not in the nutritional value Thank you

    That depends on how much your dish reduces as it cooks. The recipe as written makes 4 servings, so a serving is 1/4 of the finished dish.

  19. Aniasnina
    Loved this dish. Switched it up by adding some frozen spinach instead of peppers. Also only did 1.5oz of butter which worked perfectly since there’s already so much fat from the mayo.

    Would probably even do 3/4 cups of mayo instead of 1 cup the next time.

  20. gemma-radcliffe
    This was tasty but ended up making me sick - I think it was the overload of olive and mayo. Also - it was so, so salty. I'd definitely cut back on some ingredients next time. I'll make it again though, since it was so easy to prepare and quick to bake.
  21. Abby
    Really easy to make but so oily I couldn’t enjoy it or eat it. Love the idea of using sour cream instead. Will try this next time!
  22. gailsea73
    I loved the result, although I just used tuna in water, not olive oil. It was easy and so yummy and best of all, EASY - the only work was chopping. No doubt I should remain satiated for quite a while given the fat content!
  23. girlforthegospel
    Made this today for the first time and it was sooooo good. Also have the asparagus and walnut salad with it. Very yummy meal.
    Reply: #74
  24. Crystal Pullen Team Diet Doctor

    Made this today for the first time and it was sooooo good. Also have the asparagus and walnut salad with it. Very yummy meal.

    Wonderful! I am so glad you enjoyed these!

  25. Sherri
    Can I use light mayo instead of regular? How will it affect my keto plan?
    Reply: #76
  26. Kerry Merritt Team Diet Doctor

    Can I use light mayo instead of regular? How will it affect my keto plan?

    Light mayo is usually lower in fat and higher in sugar/carbs, which is the opposite of what you want to consume. It's super easy to make your own mayo, though. Check out our recipe! https://www.dietdoctor.com/recipes/mayonnaise

  27. debbie penner
    I used mushrooms spinach rather than peppers...I love this dish
  28. JC
    Thank you very much for the recipe. Trying it tonight. I can already taste how amazing it will be.

    This will sound like a silly question, and I can certainly improvise without an answer but...how are you suggesting the spinach specifically be served? Simply on the side, cold without dressing, just tossed in oil? Or is the casserole meant to be served on top of a bed of spinach? Just seems as an inconsequential addition, especially without a little more detail...not to mention a photo that reflects exactly as the recipe seems to suggest. Or just leave out altogether.

    I do like the idea a respondent recommended by baking the spinach inside the casserole. That sounds wonderful.

    Or...picking up on what one of the "if you liked this recipe, you may like these" photos that shows a side of baby spinach leaves with egg and tomato slices that would finish off the recipe completely all the way to the presentation stage.

    Reply: #79
  29. Kristin Parker Team Diet Doctor

    This will sound like a silly question, and I can certainly improvise without an answer but...how are you suggesting the spinach specifically be served? Simply on the side, cold without dressing, just tossed in oil? Or is the casserole meant to be served on top of a bed of spinach? Just seems as an inconsequential addition, especially without a little more detail...not to mention a photo that reflects exactly as the recipe seems to suggest. Or just leave out altogether.

    Hi JC, in any of our recipes, if we don't make a specific suggestion like for the spinach in this case, it is because we want to leave it up to you, to serve it however you prefer as it doesn't make a difference for the nutrition information. Some people prefer a little spinach salad on the side while others may prefer the texture of serving the casserole on a bed of spinach.

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