In a skillet, brown the ground beef with the diced onion until cooked through.

Drain excess fat, then stir in taco seasoning and water. Simmer for 3 minutes.

Place a tortilla in a clean skillet over medium heat.

Sprinkle a layer of cheese on one half, top with the beef mixture, and more cheese.

Fold the tortilla in half.

Cook for 2-3 minutes per side, adding a little butter to the pan for a crispy, golden finish.

Slice into wedges and serve with salsa and sour cream.