Guacamole

1 ripe avocado
1/4 c minced red onion
1 T finely chopped cilantro
1/2 T lime juice
1/4 t coarse salt
1 dash black pepper
1 small tomatillo, chopped
1 small tomato, chopped

Using a fork, mash the avocado.  
Add the chopped onion, cilantro, lime juice, salt and pepper and mix.
Just before serving, add the chopped tomato to the guacamole and mix.

Cover with plastic wrap directly on the surface to prevent oxidation.