Preheat the oven to 375°F and lightly grease a 9x13 baking dish. Warm the tortillas briefly in the microwave so they are pliable and less likely to tear.

In a skillet over medium heat, combine the black beans, cumin, half the diced red onion, and a pinch of salt and pepper. Cook for 3 to 4 minutes until warmed through and fragrant.

Spoon the bean mixture evenly down the center of each tortilla. Sprinkle about 1 tablespoon of cheese over the beans in each tortilla, then roll them up and place them seam-side down in the prepared dish.

Pour the enchilada sauce evenly over the rolled tortillas. Sprinkle the remaining cheese on top. Bake for 20 minutes until the cheese is melted and bubbly.

While the enchiladas bake, make the avocado salad. In a bowl, gently toss the diced avocados, cherry tomatoes, remaining red onion, cilantro, lime juice, olive oil, and a pinch of salt and pepper.

Remove the enchiladas from the oven and let them rest for 5 minutes. Serve each portion with a generous scoop of avocado salad on the side.