Cut the onion very finely and sweat it in oil. Clean the mushrooms, add the grated and sauté them. Scatter the flour on top, stir. Add the skinned and chopped tomatoes and the finely grated zucchini.
Pour the whole thing over with cream and season with stock powder, oregano and salt. Let it simmer for 5 minutes.
Now alternately layer the zucchini / mushroom mix and the lasagne plates in a baking dish. Finish with cheese. Bake at 180 ° C for 35 minutes.