Begin by slicing the avocado in half lengthwise and discarding the pit. You can either tap the pit gently with your knife and twist it to loosen it (while protecting your hand with a towel), or you can slice the avocado into quarters and remove the pit using your fingers or a spoon.
Next, use a spoon to scoop out the avocado flesh and transfer it to a mixing bowl.
Then, mash the avocado to desired consistency. There are several ways to mash an avocado, such as using a fork, a potato masher, or a molcajete – a traditional Mexican mortar and pestle. In this recipe, I use a fork.
Lastly, squeeze lime juice directly over the top to prevent browning. Add diced tomatoes, chopped cilantro, and onion.
Season with salt and pepper to taste, and stir just to combine.