1/8 large onion (or 1/4 small onion), finely chopped
Steps
Cut the lime half. Squeeze the juice out of the lime half using the mortar and pestle (optionally, use a lemon squeezer). Remove the peel and insides from the mortar.
Cut the avocado around the middle, leaving the seed intact.
Scoop out the insides of the avocado with a tablespoon, add it to the mortar.
Chop the onion, add it to the mortar (store the rest of it in the fridge).
Use the pestle to squash and mix all the ingredients together.
Season with a pinch of salt, and cumin.
Serve with tortilla chips, in quesadillas/tacos/burritos or in sandwiches.