Mash: Mince the garlic and place in a medium mixing bowl along with the salt. Halve and pit the avocados, and scoop the flesh into the bowl. Juice the lime over the avocados and mash everything together using a fork.
Chop: Next, slice the tomato into quarters, scoop out and remove the seeds, and then finely chop the flesh. Mince the onion and jalapeño, and chop the cilantro leaves. Add everything to the avocado mixture.
Mix: Add the cumin and mix everything together using a large spoon. Take a taste and add a pinch of extra salt, if desired.