Halve the avocado and scoop the flesh out onto a plate.
Season beginning with a big pinch each of salt, pepper, and onion powder. Squeeze the lime over the seasoned avocado.
Using a fork, mash the seasoned avocado to the consistency you like. Mix the mashed avocado, the seasonings, and lime juice together well. Taste for seasoning and adjust if needed.
To store, put guacamole in a bowl. Cover with plastic wrap, lightly pressing the plastic wrap to the surface of the guacamole, eliminating air bubbles as much as possible. Chill.