In a medium bowl, place 2 tablespoons of the chopped onion, the chiles, 1 tablespoon of the cilantro and the salt. With the back of a wooden spoon, mash until the mixture becomes a juicy paste. Place avocados in the bowl with the paste; stir to combine. Fold in the tomato and the remaining onion and cilantro. Serve with tortilla chips and cut-up raw vegetables such as jicama sticks and red bell pepper strips, if desired.