1Begin by preparing the dried guajillo chiles, dried ancho chiles, and dried arbol chiles. Remove their stems and shake out as many seeds as possible. Place the chiles in a heatproof bowl and cover them with hot water. Let them rehydrate for 20-30 minutes until soft.
2While the chiles rehydrate, prepare the aromatics. Roast the Roma tomatoes, 100 grams of the white onion, and the garlic cloves on a comal or in a dry skillet over medium heat until softened and slightly charred in spots. This will enhance their flavor.
3Once the chiles are soft, drain them, reserving about 200 grams of the soaking liquid. In a blender, combine the rehydrated guajillo chiles, ancho chiles, arbol chiles, roasted Roma tomatoes, roasted white onion, roasted garlic cloves, Mexican oregano, ground cumin, and 5 grams of the salt. Add 200 grams of the vegetable broth and blend until a very smooth sauce forms. If needed, add a small amount of the reserved chile soaking liquid to achieve a smooth consistency.
