Wash the eggplants and put into a pan (or wrap in foil) and bake until soft. Put the onions into cold water to soak and remove some of the strength. Remove the skins from the cooked eggplant and mash the pulp thoroughly. Drain the onion well and add to the eggplant. Add salt and pepper, and beat. Add lemon or vinegar alternately with the oil, and beating all the while, until you have a thick mixture. Serve in a bowl or as a side dish.