Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish or spray with nonstick cooking spray.

In a large skillet over medium heat, add the ground beef and chopped onion. Cook, stirring occasionally, until the beef is fully browned and the onion is softened, about 6–8 minutes. Carefully drain any excess grease.

Stir in the diced green chilis and ½ cup enchilada sauce. Mix until the filling is evenly coated and heated through. Remove from heat.

Spread ½ cup of enchilada sauce evenly over the bottom of the prepared baking dish.

Place one tortilla on a flat surface. Spoon about ¼ cup of the beef mixture onto the bottom third of the tortilla. Sprinkle with 1–2 tablespoons of shredded cheddar cheese. Roll the tortilla tightly and place seam-side down in the baking dish.

Continue filling and rolling the remaining tortillas, arranging them snugly in the dish.

Pour the remaining enchilada sauce evenly over the top of the rolled tortillas. Sprinkle with the remaining shredded cheese.

Bake, uncovered, for 20 minutes, or until the cheese is melted and the sauce is bubbly.

Let cool for a few minutes before serving. Garnish with chopped cilantro, sour cream, or sliced green onions, if desired.