Chop the onion and fry it in a pan with olive oil. Once it has sweated, add zucchini cut into small pieces, salt, pepper and add thyme to flavor and cook over medium heat about 20 minutes. Once the zucchinis have well reduced, add the tomatoes cut into small pieces also. Let cook over medium heat for 7 minutes.
Put the softened butter in a bowl. Add flour and parmesan and work the dough with your hands until having a crumbly dough.
Put the zucchini – tomatoes mixture in a baking dish. add the crumble dough on top. Bake 20 to 25 minutes at 200 ° C.