Combine the seasoning packet, water, and tomato sauce in a saucepan. Bring to a boil, then reduce heat and simmer until thickened.
Brown the ground beef with onion and garlic; drain excess fat. Stir in the black beans.
Add about ⅔ of the sauce to the beef mixture. Stir in a handful of cheese until melty and delicious.
Spread a little sauce in the bottom of a greased baking dish. Spoon 3 Tbsp of filling into each tortilla, roll up, and place seam-side down.
Pour the remaining sauce over the top and finish with plenty of cheese.
Bake at 350°F for 15 minutes, or until the cheese is melted and bubbly.
