Char the tomatoes, chiles and onion on a comal or hot iron skillet for 8 minutes (ish) on each side. The best flavors happen when you allow the char to be dark–very dark.
Grill the garlic for 4 minutes (ish) on each side. Take care not to burn it.
In a molcajete (mortar and pestle) grind the ingredients, starting with the salt, garlic, onion chiles, and then tomatoes. If using a blender, do not “overblend” —the tomato sauce should have a chunky texture.
Add chopped fresh cilantro and raw garlic (instead of the roasted one) for a deliciously aromatic and pungent variation.