Chop onions and cilantro and put them in a mortar.
Remove seeds and inner walls from the chili, chop it, and put it in the mortar.
Add salt and mash and mix everything thoroughly with the pestle.
Cut the avocados in half lengthwise around the pit, twist to separate, and remove the pits (save them for later)
Scoop the avocado flesh from the skins, cut into chunks, and place in a bowl.
Mash the avocados with a fork or with the pestle
Cut the tomatoes into small cubes
Put the tomatoes and the mixture from the mortar into the bowl with the avocado and mix everything well.
Season with salt and lime juice to taste.