Preheat oven to 375 degrees.
Spray a baking sheet with nonstick cooking spray and line up taco boats on the baking sheet. Spray the tops and outsides of the boats with cooking spray. Set aside.
Brown ground beef in a large skillet. Drain off all but one tablespoon of fat.
Stir in onions and cook for 4 minutes stirring frequently.
Add black beans and enchilada sauce.
Bring the mixture to a simmer and cook, stirring frequently, for 3 minutes.
Spoon mixture into taco boats and top with shredded cheese.
Bake for 10 minutes or until is melted and bubbling.
Serve with tomatoes, sour cream, avocado whatever you like!