Now make some of your favorite salsa. In terms of authenticity, salsa generally doesn't have anything more than fresh ripe tomatoes, garlic, and jalapenos (I prefer canned as opposed to raw because the flavor mixes better with the other ingredients, but you could also roast the peppers first and probably get a similar effect), or another type of chile and salt to taste. Onion is out of the question in my opinion. Pico de gallo on the other hand must have onion. Anyway, now that you have your salsa and avocados do this with them:

Squish the avocados with a fork in a bowl until slightly creamy but still chunky. Add 4 - 6 T salsa. Add lemon juice depending on taste (this is also necessary to keep avocados from browning due to oxygen). Add salt (vary to taste). Add chopped white onion.

Stir until well mixed, and eat with any Mexican dish, or just plain with chips.