1 small yellow onion (or 1/2 large onion), diced small
1 sweet bell pepper, diced small
1 (16-ounce) can black beans, drained and rinsed
1 cup frozen corn
2 teaspoons chili powder
1 teaspoon cumin
1 teaspoon kosher salt
1 1/2 cups Monterey jack, colby, or other melting cheese, shredded and divided
2 (16-ounce) jars salsa, any kind
12 to 15 medium (6-inch or so) flour tortillas
Optional: 1 cup leftover meat or extra veggies — chicken, pork, hamburger, beef, baked tofu, or roasted vegetables
In a medium bowl, mix together the onion, pepper, black beans, corn, spices, meat (if using), and just 1/2 cup of the cheese. Spread a cup or so of salsa over the bottom of a 6-quart (or larger) slow cooker, enough to evenly coat the bottom with a bit of sauce. (See the Recipe Note below for cooking in smaller slow cookers.)
Fill each of the tortillas with about 1/3 cup of the filling, roll them up as tightly as you can, and pack them seam-side down into the bottom of the slow cooker. Don’t worry if some filling falls out — just tuck it back in once you’ve set the tortilla down.
When you complete the layer, spread another cup of salsa over the top and sprinkle with about 1/2 cup of the remaining cheese. Continue rolling the remaining tortillas with the remaining filling to make one more layer; if you have leftover filling, sprinkle this over the top. Finish by pouring another cup of salsa over the top of the enchiladas. Reserve the last 1/2 cup of cheese to add later.
Place the lid on the slow cooker and cook on HIGH for 2 to 4 hours. In the last 15 minutes of cooking, sprinkle the remaining 1/2 cup of cheese over the top, re-cover the slow cooker, and finish cooking.
Serve the enchiladas with any remaining salsa. Leftovers will keep for up to a week in the refrigerator.