Dice then sauté onions in 1-2 tablespoons oil until lightly browned.
Scoop avocado flesh out of shells and remove pits. Place avocado in a large bowl or molcajete and mash with a pestle, potato masher or the back of a large spoon.
Add onion, tomatoes, chiles and spices; mix together with a fork. Taste and adjust seasoning. Stir in cilantro and lime juice.
Cover with plastic wrap laying directly on the top of guacamole to prevent exposure to air.
Serve immediately or chill 30 minutes before serving. The lime juice will help prevent browning, but guacamole is best served soon after preparing.
