Preheat the broiler. Lay the tomato and onion halves cut-side down on a foil-lined baking sheet; surround with the tomatillos and jalapeno. Broil until charred, about 5 minutes. Let cool slightly.
Meanwhile, cook the chile de arbol in a small dry skillet over medium-high heat, turning, until toasted, 30 seconds to 1 minute.
Combine the tomatoes, onion, tomatillos, jalapeno, chile de arbol, chipotle and garlic in a blender and puree until mostly smooth. Add the cilantro and puree until incorporated; season with salt. Chill at least 30 minutes before serving.
"This robust, spicy salsa is best made the day before so the rich flavors come together."
Courtesy of Food Network Magazine