This delicious and filling low carb and keto tuna casserole has no noodles, but it does have lots of flavor! Plus it’s so easy to make.
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, tuna salad, and keto tuna melt.
This low carb keto tuna casserole is so good! It has no noodles, and I promise – 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.
The ingredients you’ll need
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 because it’s lower in mercury than other tuna species.
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. I’m lazy so I chop it in the food processor.
To season: Salt, black pepper, and cayenne pepper. The cayenne pepper doesn’t make the casserole very spicy, at least not 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.
How to make keto tuna casserole
It’s so easy! Scroll down to the recipe card for the detailed instructions. Here are the basic steps:
1. Simply mix all the ingredients together, reserving some of the cheese and the parsley.
2. Then transfer the mixture to a small baking dish and sprinkle the top with the remaining cheese.
3. Bake the casserole until heated through, about 15 minutes in a 400°F oven. Garnish with parsley and serve.
Bulk it up with riced cauliflower
You can bulk up this casserole by adding 2 cups of cooked riced cauliflower, increasing the mayonnaise to 1/2 cup, and dividing it into 3 servings. But I usually don’t, because my husband and I like the casserole better without cauliflower.
What to serve with keto tuna casserole
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’s also good with a side of microwave broccoli.
What to do with leftovers?
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.
Reviews of this recipe
On Instagram, @shelikeshergreens posted this gorgeous photo of her casserole. She says, “Keto tuna casserole with sautéed green beans. I made my own mayonnaise for this. 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!”
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Keto Tuna Casserole
- 2 (5oz) cans tuna in water, drained
- 1/3 cup avocado oil mayonnaise
- 1 tablespoon Dijon mustard
- 1/2 cup shredded gruyere, divided
- 1/4 cup chopped red onion
- 1/4 teaspoon sea salt
- 1/4 teaspoon black pepper
- ¼ teaspoon cayenne pepper
- ¼ cup chopped parsley for garnish
- Preheat oven to 400 degrees F.
- Mix together the tuna, mayonnaise, mustard, 1/4 cup cheese, onion, salt, pepper and cayenne.
- Transfer the mixture to a small, 1-quart casserole dish. Sprinkle 1/4 cup shredded cheese on top.
- Bake until hot, about 15 minutes. Sprinkle with parsley and serve immediately, with cut-up veggies.