Heat the oven to 350°F. Meanwhile, make the filling.
Heat 2 tablespoons olive oil in a medium frying pan over medium heat until shimmering. Add 2 cups peeled and small-diced sweet potato, and cook until starting to soften, 7 to 8 minutes.
Stir in 1/3 cup small-diced onion, 1 minced garlic clove, and 1 seeded and minced medium jalapeño pepper if using. Cook until translucent, 2 to 3 minutes.
Stir in 1 (about 15-ounce) can drained and rinsed black beans and 1 cup frozen corn kernels. Cook until heated through, 2 to 3 minutes. Stir in 1 teaspoon smoked paprika, 1 teaspoon kosher salt, 3/4 teaspoon ground cumin, and 1/2 teaspoon black pepper. Cook until fragrant, 1 to 2 minutes. Remove the skillet from the heat.
Coat a 9x13-inch baking dish with cooking spray. Spread 1/2 cup of the red enchilada sauce on the bottom of the baking dish.
Working with one (8-inch) flour tortilla at a time, arrange 1/2 cup of the filling across the center of the tortilla. Roll the tortilla up tightly around the filling. Place seam-side down against one short side of the baking dish, tucking the ends of the tortillas underneath to close the ends. Repeat with the remaining 7 tortillas, arranging them in a tight, single layer.
Spread the remaining 1 1/2 cups enchilada sauce evenly over the enchiladas. Sprinkle with 8 ounces shredded Mexican blend cheese.
Bake uncovered until the enchilada sauce is bubbly and the cheese is melted and just beginning to brown, 20 to 25 minutes. Let cool for 5 minutes before serving. Top with sour cream, sliced avocado, chopped fresh cilantro, or thinly sliced radishes if desired.
Fresh or drained canned corn kernels can be used in place of frozen.
I like my enchiladas with a little kick to them, but if you want to make something on the mild side, skip the jalapeño or opt to use bell pepper. If you want the enchiladas to be spicier, leave the seeds in the jalapeño.
The filling can be made up to 2 days ahead and refrigerated in an airtight container. Use cold and add 6 to 8 minutes to the bake time.
The enchiladas can be assembled in the baking dish without sauce and cheese on top up to 1 day ahead. Cover and refrigerate. When ready to cook, uncover, top with sauce and cheese, and bake, adding 6 to 8 minutes to the bake time.
