Start by peeling and dicing a medium red onion. Destem and rinse the cilantro. Keep a couple sprigs for garnish then chop it and add it to a clean bowl.
If using jalapeño, deseed and devein it unless you prefer a spicier guacamole. Finely chop and add it to the bowl.
Peel the garlic, mince it, and add it to the bowl.
Carefully slice the avocados in half, remove the pits, and use a spoon to scoop the flesh into the bowl.
Mash the avocados to your desired consistency and mix with the other ingredients. Add the cumin, salt, pepper, and cayenne pepper, if using.
Squeeze in the juice of one lime and stir to combine. Taste and adjust seasoning and lime juice as needed.
Garnish with a couple of sprigs of cilantro then serve with your favorite chips.