Cut the avocados in half, remove the pits and use a spoon to transfer the avocado to a bowl. Add the cilantro, lime juice, onions, chiles, lime zest, cumin and garlic and season liberally with salt and pepper. Mash together with a fork until just combined. Taste and adjust the seasoning with salt.
Store in the refrigerator, covered with plastic wrap, until ready to serve.