1 lb ground beef

3 medium zucchinis, sliced into ¼-inch rounds

1 small yellow onion, finely chopped

2 cloves garlic, minced

1 can (14 oz) crushed tomatoes

1 tablespoon tomato paste

1 tablespoon olive oil

1 teaspoon dried basil

1 teaspoon dried oregano

½ teaspoon red pepper flakes (optional)

Salt and black pepper, to taste

1 ½ cups shredded mozzarella cheese

½ cup grated Parmesan cheese

Optional Add-ins: 1 cup sliced mushrooms, ½ cup chopped bell pepper, ½ cup ricotta or cottage cheese

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Preheat the oven to 375°F (190°C) and grease a 9×13-inch baking dish.
Slice zucchini and lay on paper towels. Sprinkle lightly with salt and let sit for 10 minutes. Pat dry to remove excess moisture.
In a skillet over medium heat, sauté onion in olive oil for 2-3 minutes. Add garlic and cook for 1 more minute. Add ground beef and cook until browned. Drain any excess fat.
Stir in crushed tomatoes, tomato paste, basil, oregano, chili flakes (if using), salt, and pepper. Let the mixture simmer for 5-7 minutes to allow the flavors to meld together.
Layer the sauce and zucchini slices in the prepared baking dish, alternating the two and ending with sauce on top. Sprinkle the shredded mozzarella and grated Parmesan cheese over the top.
Bake uncovered for 25–30 minutes or until the casserole is bubbly and golden. For a crispier top, broil for an additional 2-3 minutes.
Let the casserole rest for 10 minutes before serving to ensure the best texture and ease of serving.

For extra creaminess, layer ricotta or cottage cheese between the zucchini and beef layers.
To make this dish keto-friendly, reduce the amount of tomato sauce and add cream cheese to the beef mixture for a richer, lower-carb option.
For a vegetarian version, replace the ground beef with a plant-based meat substitute or use a mix of mushrooms, bell peppers, and zucchini.
This casserole is naturally gluten-free, making it a great option for those with gluten sensitivities.