In a medium mixing bowl, mash up the avocados with a fork. Make them as smooth as you like. (I prefer them a little on the chunky side.)
Add the tomato, onion, cilantro, and garlic powder. Mix to combine. Season with salt and pepper to taste.
Transfer to a serving bowl and serve with your favorite tortilla chips. Store leftovers in an airtight container in the fridge with the avocado pit in the guacamole to help prevent browning.