Preheat the oven to 425F. Spray a 9 x 11-inch baking dish with cooking spray.
Place about ⅓ cup of the cheese in the center of the tortilla. Roll and place seam side down in the baking dish. Repeat until all tortillas are filled, arranging them in baking dish with ¼ inch in between.
Pour ¼ cup sauce over each enchilada, and sprinkle evenly with grated cheese and onion, if desired.
Bake for 7 to 10 minutes, until the cheese is melted and the sauce is bubbly.
Garnish with a little more cheese. Serve immediately.
Classic Tex-Mex Chili Gravy:
In a blender jar, combine the onions, garlic, and ½ cup water. Process on high speed for 1 minute, or until smooth.
In a small saucepan over low heat, combine the crumbled beef, 2 cups water, and the processed onion and garlic. Simmer, uncovered, for 30 minutes. Using a large spoon, skim the frothy substance that rises to the surface; discard. Repeat 2 or 3 times during the cooking time. Also use the spoon to break up clumps of meat for a smooth consistency. Set aside off the heat.
In a large skillet over medium heat, heat the oil until it shimmers. Lower the heat. Stirring continuously, add the flour and cook until the flour turns a light golden color. Set aside off the heat.
In a medium saucepan over low heat, heat the broth and 1 cup water until steaming hot, almost boiling. Meanwhile, in a small bowl or container with a lid, combine the chili powder, salt, Holy Trinity, and cayenne pepper, whisking or shaking to blend. Stir the combined spices into the hot broth mixture, blending until smooth.
Gradually add the cooked beef and chili powder–broth mixture to the cooked flour, stirring constantly to remove lumps. Stir and cook over low heat for 5 minutes, or until the mixture is almost as thick as ketchup.
Set aside off the heat for at least 10 minutes to let the flavors mellow before serving.
The sauce may be refrigerated for up to 1 week or frozen for up to 3 months.
Enchilada Queen Secret Chile Sauce for Flavoring Tortillas:
Rinse the chiles with cool water.
In a medium saucepan over high heat, combine the chiles and 1 ¾ cups water. Bring to a boil, then reduce the heat and simmer for 15 minutes. Set aside off the heat for 10 minutes.
In a blender jar or work bowl of a food processor, process the cooked chiles and their liquid until smooth, about 1 minute.
Pour the pureed chile mixture through a fine strainer into a small bowl, pressing with the back of a spoon to extract as much liquid as possible; discard the solids.
Cover the sauce and put in the refrigerator to chill, then use to flavor tortillas.
To store and reuse the chile sauce, strain out any pieces of tortilla before pouring into a clean, covered container.
The flavoring sauce may be refrigerated for up to 1 week or frozen for up to 6 months. Thaw completely and stir before using.