In the bowl of a blender put the onion cut into chunks and caviar. Passaged to form a homogeneous mixture. Add the bread, garlic, grated rind of 1 lemon and the juice of lemon and a half and mix with a mixer. To the mixture was added to the oil stream while stirring. Taste and put in a bowl, cover with foil and leave in the refrigerator for at least 1 hour. Serve decorated with black olives.