Heat the olive oil in a skillet over medium heat. Add your ground beef or turkey and break it apart with a spatula. Once it’s mostly browned (about 7–8 minutes), toss in the diced onion and garlic. Cook another 3–4 minutes until the onion softens and everything smells fragrant.
Sprinkle in your taco seasoning, stirring briefly to toast the spices (about 30 seconds). Then pour in the enchilada sauce, black beans, and corn. Let this mix simmer for around 5 minutes, so the flavors meld and excess liquid reduces slightly. Taste and adjust salt or spice if needed.
Preheat your oven to 375 °F (190 °C). Lightly grease a 9×13-inch baking dish (or similar). Spread a thin layer of enchilada sauce on the bottom — this keeps the first tortilla layer from sticking.
Arrange tortillas across the sauce base, tearing them as needed to cover completely. Spoon over a portion of the meat-bean mixture, and sprinkle on cheddar and Monterey Jack. Continue layering (tortilla → meat mix → cheese) until ingredients finish. End with a top layer of tortillas and a final generous layer of cheese.
Cover the dish with aluminum foil (spray underside lightly or use parchment so cheese doesn’t stick). Bake covered for 20 minutes. Then remove the foil and bake another 10 minutes, or until the cheese is bubbling and lightly golden at the edges.
Once out of the oven, give it 5–10 minutes to rest. This helps the layers firm up so slices stay intact when serving. Then cut into squares and get ready for the show.