Scoop the avocado into a bowl and mash it with a fork. Mash it more or less depending on if you like a chunky or smooth guacamole. Add the olive oil to make a smoother consistency.
Add the lime juice, salt, diced onion, basil, tomato, garlic and cayenne pepper. Stir to combine.
Serve immediately or store in an air tight container in the fridge for up to 24 hours. Guacamole is best if served as soon as it is made as possible but the lime juice will help prevent it from turning brown.