Meanwhile, combine black beans, chili powder, and zest and juice of the lime. Lay the tortillas out on the counter or table and divide the seasoned beans among them. Roll each enchilada and put seam-side down in the casserole dish. Pour the cheese sauce down the middle of the enchiladas. That way the edges are unsauced and get fabulously crispy. Bake for 30 minutes. Serve with salsa fresca, sour cream, and avocado.