In northern Mexico, enchiladas often are made by layering tortillas with cheese and onions. Check your local specialty market for chiles and queso fresco.
1. Combine cheddar cheese and onions in a small mixing bowl. Heat 1" oil in a large skillet. Fry tortillas one at a time until edges are crisp, about 30 seconds. Drain on paper towels.
2. To assemble, ladle some sauce in the center of a plate. Coat a tortilla with sauce by dipping in saucepan, place on plate, and cover with 1⁄4 cup cheese–onion mixture; repeat twice, and top with a fourth dipped tortilla. Keep warm in a low oven while you assemble other plates. When ready to serve, spoon a bit more sauce over each enchilada and top with queso fresco.