Preheat your oven to 375°F (190°C).
Heat olive oil in a large skillet over medium heat. Add the chopped onion and sweet green peppers. Sauté for 5-7 minutes until they become soft and fragrant.
Add the garlic and cook for another 1-2 minutes, stirring to release the flavors.
Stir in the diced tomatoes, tomato paste, black pepper, paprika, and dried basil. Let the mixture simmer for 5 minutes, allowing it to thicken slightly.
In a large casserole dish, combine the sautéed vegetables with the zucchini cubes and season with salt to taste. Mix everything together until well combined.
Sprinkle the grated cheese evenly over the top of the casserole.
Bake for 20-25 minutes, or until the zucchini is tender and the cheese has melted and is golden.
Let it cool for a few minutes before serving, and enjoy!