Preheat the broiler.

In a large frying pan, heat 1 tablespoon of olive oil over medium heat.

Add the chopped onion and sauté until golden brown.

Add the crushed garlic to the pan and sauté for 1 minute longer.

Add the shrimp to the pan and sauté for approximately 3 minutes until they turn pink and are cooked through.

Transfer the cooked shrimp to a casserole dish.

In the same frying pan, add the remaining 1 tablespoon of olive oil, tomato sauce, and dried basil.

Simmer for 15 minutes, then season with salt and pepper to taste.

Pour the tomato sauce mixture over the shrimp in the casserole dish.

Sprinkle the grated mozzarella and Parmesan cheese over the top.

Place the casserole under the preheated broiler and cook until the cheese is bubbly and golden brown, about 5 minutes.

Serve hot, optionally with rice.