I've never had much luck with homemade guacamole until reading this book. The trick is to rinse the minced onion before adding it to the guac- rinsing removes that bitter onion taste that has historically taken over any of my aspiring guacs or salsas.
Gently chop into large bits in food processor:
1 large tomato
1 serrano or jalapeno chile
1-2 garlic cloves
3 TB chopped cilantro
Scoop into a serving dish and set aside.
Mince ½ a white onion in clean food processor. Dump minced onion into strainer and rinse under water. Add ½ C of the rinsed minced onion into serving dish with the tomato mixture.
Halve 3 large ripe avocados, remove pits. Using dull table knife, cut a checkerboard pattern into cut side of guac, then use spoon to scoop out into serving dish.
Use back of spoon to coarsely mash avocado. Stir in 2-3 tea of lime or lemon juice and up to 1 teaspoon of salt.
Serve with tortilla chips!