Put the tomato, if using, onion, chile, lime juice, and cilantro (coriander) in a bowl, stir well to mix, and season with salt. Gently fold in the avocado, then taste and adjust the seasoning, if necessary. Add the olive oil and mix. Serve with tortilla chips.
Note: It is best to prepare guacamole minutes before serving to avoid discoloration. Instead of incorporating the chopped tomato you can use it as a garnish, arranging it around the edge of the serving bowl.