Peel the onions, remove the seeds from the pepper, and cut the ends of the aubergine and pumpkin. Then slice all the vegetables as thinly as possible.
For the tomato sauce
Put the onion in a large pan with a little vegetable oil and fry it lightly.
Add the garlic and cook for a few minutes before adding the tin of chopped tomatoes.
Add ½ teaspoon of salt, ½ teaspoon of sugar and the cayenne pepper, then cover the pan and cook slowly for 10 minutes.
To prepare the dish
Pour the tomato sauce into a deep dish suitable for the oven, and add the béchamel sauce on top.
Arrange the slices of fruit and vegetables in turn to create a colorful row in the sauce. Do not lay them flat; put them on their sides so they stand upright.
Continue until the dish is full and you have used all the vegetables.
Bake in the oven for 1 hour, or until the vegetables are cooked and soft.