1. Preheat the oven to 375°F or 190°C.

2. In a large mixing bowl, combine 250g of chopped tomatoes, 1 teaspoon of salt, and a pinch of pepper. Mix well and set aside.

3. In a separate bowl, combine 250g of fresh gnocchi and 60g of grated parmesan cheese. Gently mix until the gnocchi are evenly coated with the cheese.

4. In a large skillet, cook the meatballs over medium-high heat until browned on all sides, about 5-7 minutes. Drain the excess fat and add the tomato mixture. Simmer for an additional 5 minutes.

5. In a 23x33cm or 9x13-inch baking dish, create a layer of the meatball and tomato mixture. Arrange half of the gnocchi on top, followed by half of the remaining tomato sauce. Repeat the layers, finishing with a layer of tomato sauce on top.

6. Sprinkle the remaining parmesan cheese evenly over the top of the gratin. Cover with aluminum foil and bake for 25 minutes.

7. Remove the foil and continue baking for an additional 10-15 minutes, or until the cheese is golden brown and bubbly.