Cut the eggplant into thin small slices and lay the slices on paper towels. Sprinkle with salt - to extract the bitter juices – and leave for about 20 mins.
Heat olive oil in a heavy frypan and fry eggplant in batches until golden–to dark brown. Add to oil to the pan as needed during cooking as eggplant absorbs a lot of oil. Remove slices from oil and put on paper towel to drain. While the eggplant slices are still hot, sprinkle them with a little extra salt and ground pepper.
Chop the parsley finely and chop the tomatoes into cubes. Mix eggplant, parsley and tomatoes and the Spanish onion - if using - together. Sprinkle the salad with lemon juice and some chillie powder and mix well until all the ingredients are coated.
It is best to make the salad an hour before serving to let all the flavours combine well.