Heat grill or griddle over medium-high heat. Spray with non-stick spray and add onion and jalapeño and grill for 2-3 minutes (or until there are grill marks) and then flip. Add tomatoes to grill and cook all veggies for an additional 2 minutes. Remove from grill to cool. When cooled, dice veggies.
Add avocados and lime juice to a bowl. Mash avocados with a fork. Add onion, jalapeño, tomato and cilantro to bowl and stir to combine.
Add cumin, salt, pepper and red pepper flakes and stir to combine. Serve with your favorite tortilla chips!