Salsa Roja

From Tu Casa Mi Casa: Mexican Recipes for the Home Cook by Enrique Olvera
Makes 2 cups
 
6 tomatoes
½ medium onion
2 serrano chiles, or to taste
1 large garlic clove
Salt
Heat a frying pan or comal over high heat.  Place the tomatoes, onion, serranos, and garlic on the pan and char on all sides, about 20 minutes.  Remove from the heat, let cool to room temperature, and mash in a molcajete or pulse in a blender until chunky.  Serve at room temperature or refrigerate up to 1 week.