It happened again so I have to discuss this again.
Avocado is a very delicate fruit. Please don't mix it with raw white onions, it can't meet onions on the field of battle and retain any flavor of its own. Guacamole made in this way is slimy onion sauce. ick.

To make unbelievably GOOD, Avocado flavored guacamole:
Take an avocado or two - scoop it out into a bowl.
Use a fork to mash it up.
Add salt and pepper and, if you are feeling kind of randy, a bit of garlic powder.
Add the juice of about 1/4 of a lemon.
Mix. Serve. That's it, that's all.
Try it. love it, be converted to this idea and stop the onion-y slime!