Put the whole eggplant into a moderate oven. Bake until the dried skin cracks and the eggplant are soft when pressed with the finger. Blanch the tomato quickly in boiling water to remove the skin, seed it, dice the flesh. Skin the eggplant, put through a medium vegetable mill or, even better, chop them with the tomato flesh. Mash the onions or shallot and the garlic in a garlic press. Put all the ingredients into a salad bowl, salt, pepper, stir with a wooden spoon, adding the oil slowly as for a mayonnaise. Stop adding oil as soon as the paste is sufficiently thickened. Chill. Add dill or parsley when serving.
