1. FOR THE GRAVY: Toast chiles and cumin in 12-inch skillet over medium-low heat, stirring frequently, until fragrant, about 2 minutes. Transfer to spice grinder and let cool for 5 minutes. Add garlic powder and oregano and grind to fine powder.

2. Heat oil in now-empty skillet over medium-high heat until shimmering. Whisk in flour, 1/2 teaspoon salt, 1/2 teaspoon pepper, and spice mixture and cook until fragrant and slightly deepened in color, about 1 minute. Slowly whisk in broth and bring to simmer. Reduce heat to medium-low and cook, whisking frequently, until gravy has thickened and reduced to 1 1/2 cups, about 5 minutes. Whisk in vinegar and season with salt and pepper to taste. Remove from heat, cover, and keep warm. (Sauce can be made up to 24 hours in advance. To reheat, add 2 tablespoons water and microwave until loose, 1 to 2 minutes, stirring halfway through microwaving.)

3. FOR THE ENCHILADAS: Adjust oven rack to middle position and heat oven to 450°F. Brush both sides of tortillas with oil. Stack tortillas, then wrap in damp dish towel. Place tortillas on plate and microwave until warm and pliable, about 1 minute.

4. Spread 1/2 cup gravy in bottom of 13 x 9-inch baking dish. Combine cheeses in bowl; set aside 1/2 cup cheese mixture for topping enchiladas. Place 1/4 cup cheese mixture across center of each tortilla, then sprinkle each with 1 tablespoon onion. Tightly roll tortillas around filling and lay them seam side down in dish (2 columns of 6 tortillas will fit neatly across width of dish). Pour remaining 1 cup gravy over enchiladas, then sprinkle with reserved cheese mixture.

5. Cover dish with aluminum foil and bake until sauce is bubbling and cheese is melted, about 15 minutes. Let enchiladas cool for 10 minutes, then sprinkle with remaining onion. Serve.

Serves 6