Pit the avocados and scoop into a bowl using a spoon.
Mash the avocado using a fork or potato masher then add the onion and chopped tomato.
Stir in lime juice then season to taste with salt.
Serve the guacamole immediately with tortilla chips.
Notes
For the best guacamole texture, mash the avocados just until creamy but still slightly chunky. Over-mashing can make the guacamole dense instead of light and scoopable.