Start by cutting the ripe avocado in half lengthwise. Remove the pit carefully, and scoop the flesh into a mixing bowl using a spoon.
Using a fork or potato masher, mash the avocado to your desired consistency. For a chunky guacamole, mash lightly. If you prefer it smoother, go ahead and mash it more thoroughly.
Pour in the freshly squeezed lime juice. This not only adds flavor but also helps prevent the avocado from browning.
Add the diced red onion to the bowl. Mix well to ensure that every bite has a hint of onion.
Chop the cilantro finely and add it to the mixture. This herb is key to achieving that fresh taste that guacamole is known for.
Gently fold in the quartered grape tomatoes. They should be mixed in delicately to maintain some of their juiciness.
Finally, sprinkle in a pinch of salt and black pepper. Adjust to your preference, and give it one last stir.
Transfer the guacamole to a serving bowl, and garnish with additional chopped cilantro if desired. Serve with tortilla chips, fresh veggies, or use it as a topping for tacos or burritos.