Take one eggplant or more roast it in a old pan with oil. It is advisable that the pan would have ribs so that eggplant won't be cooking in its own juices.
During the roasting, make holes in the eggplant with a fork, the steam accumulates in it and needs to get out.
After the eggplant is absolutely soft and most of its peel is blackened, put the eggplant on a board and cut it lengthwise. Keep the flesh of the eggplant and remove all the burned skin.
Mince the eggplant with a knife to a purée, keeping the seeds whole. The cutting should be done with a stainless steel chopper or wooden chopper. (In my opinion it is best to use a stainless steel chopper).
Pass the roasted eggplant into a glass or plastic bowl and add between half a spoon to one full spoon of oil for every eggplant, and salt according to ones own taste. Then chop the onion in small pieces and add it in the eggplant salad.