This delicious and filling tuna casserole has no noodles, but it has plenty of flavor!
Ready in just 30 minutes and using simple everyday ingredients, this easy keto recipe is perfect for a weeknight dinner.
Canned tuna is one of my favorite ingredients. It's tasty, filling, and very affordable. And just as important - I always have it on hand, making it the natural choice when the fridge is otherwise bare. I use it to make tuna cakes and tuna salad.
I also use it to make this tuna casserole. It's so good! It has no noodles, but you won't miss them. It's a lazy casserole - minimal chopping necessary. And it's ready fast, so it's perfect for weeknight dinners.
This is a delicious, filling, well-seasoned mixture of canned tuna, chopped red onion, mayonnaise, and cheese, baked until golden and bubbly. Here's an overview of the ingredients - the exact measurements are listed in the recipe card below:
Canned tuna: I use skipjack tuna in this recipe.
Mayonnaise: I like using avocado oil mayonnaise. My favorite brand is Sir Kensington's.
Dijon mustard: It's creamier and less vinegary than yellow mustard. I do recommend using it here rather than using yellow mustard.
Shredded Gruyere cheese: Other melty cheeses such as cheddar or provolone should work too. But Gruyere is especially flavorful.
Chopped red onion: Make sure it's finely chopped.
To season: Salt, black pepper, and cayenne pepper. The cayenne pepper doesn't make the casserole very spicy, at least to my palate, but it does add a nice subtle kick.
Chopped parsley: I use it mostly for garnish, so you can skip it if you don't have it on hand. It does add a nice splash of color, though.
Making this tuna casserole is so easy! Scroll down to the recipe card for detailed instructions. Here are the basic steps:
Simply mix all the ingredients together, reserving some of the cheese and the parsley.
Next, transfer the mixture to a small baking dish and sprinkle the top with the remaining cheese.
Bake the casserole until heated through, about 15 minutes in a 400°F oven. Garnish with parsley and serve.
You can bulk up this casserole by adding 2 cups of cooked riced cauliflower, increasing the mayonnaise to ½ cup, and dividing it into 3 servings.
Frequently asked questions
This casserole can become dry if the ratio of tuna to creamy ingredients (mayonnaise and mustard) is too high.
I find that ⅓ cup of mayo works well, but depending on the brand of tuna you use, you might need to increase it and use up to ½ cup.
Yes! I do it all the time. It's a different recipe than classic ones, and you'll want to serve it with something for scooping it out, such as fresh-cut veggies, crackers, or pork rinds. But it's very, very good.
Yes. Once completely cool, you can wrap the baking dish in plastic wrap followed by a layer of foil. Freeze it for up to three months. Thaw it in the fridge.
I love this recipe as is and almost always make it as written. But in case you'd like to vary the basic recipe, here are a few ideas for you:
- You can use tuna in olive oil instead of tuna in water. It's delicious.
- Try using sour cream instead of mayonnaise.
- As mentioned in the review below, dill makes a nice addition to this recipe.
- Sharp cheddar or provolone are good substitutes for gruyere. Smoked gouda is also good.
On Instagram, @shelikeshergreens posted this gorgeous photo of her casserole. She says, "I made my own mayonnaise for this casserole. I didn’t have gruyere so I used cheddar instead. I added dill to the mix to bring some freshness into it. This was amazing with the sautéed beans!"
This casserole is rich and filling. As you can see in the recipe card below, a serving has 465 calories. So I simply serve it with fresh-cut veggies for scooping it out of the baking dish (or plate). It's also good with a side of microwave broccoli.
Leftovers keep well in the fridge for 3-4 days, or you can freeze them for up to three months if you want to keep them for longer. Gently reheat them in a 300°F oven, or in the microwave on 50% power.
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Keto Tuna Casserole
- 2 (5 oz) cans tuna in water, drained
- ⅓ cup avocado oil mayonnaise
- 1 tablespoon Dijon mustard
- ½ cup shredded gruyere cheese divided
- ¼ cup minced red onion
- ¼ teaspoon sea salt
- ¼ teaspoon black pepper
- ¼ teaspoon cayenne pepper
- ¼ cup chopped parsley for garnish
- Preheat your oven to 400 degrees F.
- Mix together the tuna, mayonnaise, mustard, ¼ cup cheese, onion, salt, pepper, and cayenne.
- Transfer the mixture to a small, 1-quart casserole dish. Sprinkle the remaining ¼ cup shredded cheese on top.
- Bake until hot, about 15 minutes.
- Sprinkle with parsley and serve immediately, with cut-up veggies and/or pork rinds for scooping out.