Onions peel and quarter. Clean, wash and dry the tomatoes. Drain feta and cut into slices. Put 1/4 of each vegetable on a piece of aluminium foil. Sprinkle each with 1 teaspoon of sugar and sprinkle each with 1 tablespoon of vinegar.
Place the slices of feta on top. Close the packet on the sides and place it on a fat pan of the oven. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 20 minutes. Serve vegetable parcels with 1 teaspoon of pesto each. Flatbread tastes good with them