First, toast the arbol chiles in a comal, only 3 seconds, do not spend more time because it could change the flavor.
To boil the tomatillos and the tomato in water, make a small cross in the tomato with a knife so that later we can remove the skin
When they are cooked add them to the blender along with the chilies, garlic and salt to taste
Bring the sauce back to a boil for even more flavor and voila