Preheat the oven to 375°F (190°C).
In a large skillet, cook the ground beef and diced onion over medium heat until the beef is browned and the onion is soft. Drain any excess fat.
Stir in the taco seasoning and 1/4 cup of water. Let it simmer for a few minutes.
Spread 1/2 cup of enchilada sauce over the bottom of a 9x13 inch baking dish.
Place a portion of the beef mixture and some shredded cheese in each tortilla, roll them up, and place them seam-side down in the baking dish.
Pour the remaining enchilada sauce over the rolled tortillas and sprinkle with the remaining shredded cheese.
Bake in the preheated oven for 20-25 minutes until the cheese is melted and bubbly.
Serve the enchiladas hot, garnished with your favorite toppings such as sour cream, chopped cilantro, or sliced jalapeños.