1. preheat stove to 260 degrees.
Remove skins from onions and cut in half, then into thin slices. Rinse them several times in cold water, squeezing gently. Set aside in a baking dish.
3. rinse the tomatoes, pat dry and brush lightly with oil. Steam in a small ovenproof baking dish in the oven for 15 min until the skin is wrinkled and charred. Remove and cool briefly. Then remove the skin exactly. Roughly mash the flesh with a fork or possibly a spoon.
Mix onions and tomato pulp together in a small serving bowl.
Season with salt to taste and bring to the table.