Peel the onion and chop it into fine cubes. Grill the aubergines in a grill pan or in the oven at the highest temperature until the skin is black all over. Let cool and peel off the skin.
The pulp with the help of a non-metallic cleaver e.g., finely chop with a wooden knife and place in a mixing bowl. Add a little oil and stir in vigorously with a wooden spoon. Gradually add the oil in a thin stream, stirring vigorously, until the puree is creamy. Stir in the onions and season with salt and pepper.
If too much oil is used, it can no longer be bound and floats to the surface. Soak up excess oil with a piece of kitchen paper. Garnish with halved cherry tomatoes if desired.
1 serving is enough for a medium-sized salad bowl. It is served with white bread in Romania.