Core tops of tomatoes and cut an "x" in the bottom of the skin. Place in boiling water for 2-3 minutes - immediately remove and place in an ice bath. Allow tomatoes to cool and (easily) take off skins.
Puree tomatoes in a blender. Pour into a large stock pot.
Roughly chop the remaining ingredients, reserving 1 red onion and 1/2 bunch cilantro for the end. Place ingredients in the blender and puree. Add to tomato mixture in stock pot.
Put stock pot over medium heat until mixture lightly boils. Reduce heat to low and simmer for 3-4 hours, until salsa has reduced by about 1/3. Stir occasionally.
Cool salsa. Puree reserved red onion and cilantro in your blender and mix into salsa. Pour into quart-sized freezer bags (this recipe made roughly a gallon of salsa for me). Freeze for up to 6 months.