Make sure your kitchen is well ventilated. Put a piece of foil in a heavy saute pan and set it over medium-high heat.
Place the whole tomatoes, chile and garlic cloves in the pan and dry-roast them on all sides until well charred and soft. The garlic and chiles will be done quickly; the tomatoes may take 10 minutes or longer to cook.
Peel the garlic and stem the chile. Place the tomatoes, garlic and chile in a food processor with the onion, salt and cilantro. Pulse until the salsa is smooth and taste for seasoning.
This salsa will keep, refrigerated, for several days.
Deborah Schneider is a chef and author of the award-wining ¡Baja! Cooking on the Edge (Rodale) and Cooking with the Seasons (STC), nominated for a 2009 James Beard Award. She is the executive chef and partner in SOL Cocina in Newport Beach, California. Schneider lives with her family in San Diego.