This gratin layers sautéed zucchini rounds with canned tuna in a heavy cream mixture, then covers everything with mozzarella and Parmesan. It bakes in a 9×9-inch dish until the top is bubbly and golden brown. The recipe takes 45 minutes in total, 15 for prep and 30 for cooking, and makes 4 servings.
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Most of the work is slicing the zucchini and a quick sauté. The assembly is two layers, and the oven does the rest.
What Goes in the Dish
The card has the full amounts. A few notes on the ingredients:
- Zucchini (2 medium): sliced into thin rounds.
- Tuna (one 5-ounce can): packed in olive oil and drained. Any canned tuna works, but squeeze out the excess liquid so the gratin does not turn watery.
- Heavy cream (1/2 cup): mixed with the tuna, oregano, salt and pepper to make the creamy layer.
- Mozzarella (1 cup) and Parmesan (1/4 cup): mozzarella melts across the layers and Parmesan finishes the top.
- Garlic (2 cloves) and olive oil (1 tablespoon): sautéed first to flavor the zucchini.
- Parsley (1/4 cup, chopped): a garnish at the end.
Slicing and Sautéing the Zucchini
Slice the zucchini into thin rounds, about 1/4 inch thick, so they cook evenly. A mandoline makes this faster and keeps the slices uniform.
Heat the olive oil in a large skillet over medium heat. Add the garlic and cook for about 1 minute, until fragrant. Add the zucchini and cook for 5 to 7 minutes, stirring now and then, until it is slightly softened but still has a bit of crunch. Do not cook it further than that, because it keeps cooking in the oven.
Layering and Baking
Mix the drained tuna with the cream, oregano, salt and pepper until the tuna is coated. In a greased 9×9-inch baking dish, layer half of the zucchini, then half of the tuna mixture, then half of the mozzarella. Repeat with the rest of the zucchini and tuna mixture, and top with the remaining mozzarella and the Parmesan.
Bake at 375°F (190°C) for 25 to 30 minutes, until the cheese is bubbly and golden brown. Let it cool for a few minutes before serving so the layers set, then sprinkle with parsley.
Swaps and Add-Ins
- Sun-dried tomatoes or olives: chopped and mixed in with the tuna.
- Other proteins: canned salmon or shredded chicken in place of the tuna.
- Herbs: fresh basil or thyme.
- Cheese: cheddar for a sharper flavor, or a sprinkle of feta.
What to Serve With It
A side salad of mixed greens, cucumbers and cherry tomatoes with an olive oil and vinegar dressing cuts through the creamy gratin. Steamed broccoli or cauliflower seasoned with salt and pepper also works. To drink, try sparkling water with lemon or lime, or a glass of dry red or white wine such as Cabernet Sauvignon or Sauvignon Blanc.
Nutrition per Serving
Each serving has approximately 290 calories, 20 grams of fat (10 grams saturated), 4 grams of carbohydrates, 1 gram of fiber, 1 gram of sugar, 24 grams of protein and 500 milligrams of sodium. These are estimates.
FAQ
Can I use fresh tuna instead of canned?
Yes, but cook it thoroughly before mixing it with the other ingredients.
How do you store leftovers?
Keep them in an airtight container in the refrigerator for up to 3 days. Reheat in the oven or microwave until warmed through.
Can I make it ahead or freeze it?
You can assemble the gratin a day ahead and keep it in the refrigerator until you are ready to bake. You can also freeze it assembled but unbaked. Cover it tightly with plastic wrap and aluminum foil, thaw it in the refrigerator overnight, and bake as directed.
What can you substitute for heavy cream?
Full-fat coconut milk, or a mix of Greek yogurt and water.
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Written and edited by The Foodie Yummy Kitchen Team
The Foodie Yummy Kitchen Team writes and edits the recipes on Foodie Yummy: classic American potluck salads, holiday sides and easy comfort food, with a few low-carb options. Every recipe lists exact quantities, numbered steps and a printable recipe card, plus notes on swaps, storage and make-ahead timing. Spot a problem with a recipe? Tell us through the contact page and we will correct it. About us
Keto Zucchini & Tuna Gratin: A Delicious Low-Carb Delight!
Ingredients
Instructions
Preheat the oven to 375°F (190°C).
In a large skillet, heat the olive oil over medium heat. Add the minced garlic and sauté for about 1 minute until fragrant.
Add the sliced zucchini to the skillet and cook for 5-7 minutes, stirring occasionally, until the zucchini is slightly softened. Remove from heat.
In a mixing bowl, combine the drained tuna, heavy cream, oregano, salt, and black pepper. Mix well.
In a greased 9×9-inch baking dish, layer half of the zucchini slices on the bottom. Spread half of the tuna mixture over the zucchini, then sprinkle with half of the mozzarella cheese.
Repeat the layers with the remaining zucchini, tuna mixture, and top with the remaining mozzarella and Parmesan cheese.
Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it cool for a few minutes. Garnish with chopped parsley before serving.
Notes
For added flavor, consider mixing in some chopped sun-dried tomatoes or olives with the tuna.
You can substitute the tuna with canned salmon or shredded chicken for a different protein option.
Nutrition
| Serving Size | 1 serving |
|---|---|
| Calories | 290 calories |
| Sugar Content | 1g |
| Sodium Content | 500mg |
| Fat Content | 20g |
| Saturated Fat Content | 10g |
| Unsaturated Fat Content | 8g |
| Trans Fat Content | 0g |
| Carbohydrate Content | 4g |
| Fiber Content | 1g |
| Protein Content | 24g |
| Cholesterol Content | 70mg |