Preheat your oven to 350°F.

In a large skillet, cook the ground beef and chopped onion over medium heat until the beef is browned and the onions are tender.

Drain any excess fat from the skillet.

Stir in 1 cup of enchilada sauce and 1 cup of shredded cheddar cheese into the beef mixture until well combined.

Lay out the flour tortillas and distribute the beef mixture evenly along the center of each tortilla.

Roll up the tortillas tightly and place them seam side down in a 9x13 inch baking dish.

Pour the remaining enchilada sauce over the rolled tortillas, making sure they are completely covered.

Sprinkle the remaining 1 cup of shredded cheddar cheese over the top of the sauce-covered tortillas.

Bake in the preheated oven for about 30 minutes, or until the cheese is melted and bubbly.