1/2 serrano pepper or jalapeño, deseeded and finely chopped
Scoop the flesh of the avocados into a mortar and roughly mash with the pestle. If you don’t have a mortar and pestle, use a bowl and mash the avocado with the back of a fork.
Add the onion, cilantro, lime juice, and serrano or jalapeño pepper. Stir to combine with a spoon. Taste and season with salt to taste. Add more lime juice if necessary. Eat with lots of salty tortilla chips.