Scoop out avocados into a large bowl, reserving 2 of the pits. Mash avocado until semi smooth with a few chunks left. Chop and add tomato and onion. Add remaining ingredients and stir. Taste and adjust seasonings as necessary.
Place reserved pits in guacamole and refrigerate until serving time. Remove pits and serve with salted tortilla chips (for dipping). The pits prevent the guacamole from turning dark.