Dice the tomatoes, onion, and cilantro and combine in a bowl. There should be a little less onions than tomatoes, and add enough cilantro so that there is plenty of green, but that it doesn’t overpower the mix.
Mince the garlic and add to the bowl.
Roll the lime on a hard surface to loosen the pulp (microwaving for 10 seconds helps too). Slice it in half and extract the juice. Add to the tomato mix.
Stir all of the ingredients, salt and pepper to taste. Add more lime if it tastes bland. This can be made the night before if you’d like.