Preheat oven to 400. Place enchilada sauce and green chiles in a medium sauce pan and simmer over medium-high heat while you prepare the enchiladas.
Add black beans, avocados, onions, garlic salt, cumin, chile powder, cilantro and tomatoes to a large bowl and stir to combine. Add about 1 cup of sauce into the bottom of a large baking dish. Spoon about 3 tablespoons of black bean-avocado mixture into the centre of each tortilla, roll it up tightly and place in prepared dish on top of sauce. Lay each side by side, seam side down.
Pour remaining sauce over rolled enchiladas. Sprinkle cheese evenly over enchiladas and top with any left over filling. Bake 15-20 minutes until cheese is bubbly. Serve warm.