For the topping, heat around 6 tablespoons of oil, and according the recipe fry 1kg of sliced onions until soft, add a clove of garlic, 400gm canned tomatoes and 15ml of tomato puree. Let simmer for about 20 minutes.
Top with some cheese, 100gms should be fine. Here I used only cheddar, again, though it was good, but I'd like to try it gooey, so next time I'll take one part mozzarella and two parts cheddar. Then put it back in the oven till the cheese melts (of course cheddar doesn't melt!).