Prepare the Filling:
Heat a tablespoon of olive oil in a large skillet over medium-high heat. Add the ground turkey and diced red onion and cook until the turkey is browned and the onion has softened. Add the diced jalapeño and garlic and cook for one more minute until fragrant.

Build the Flavorful Sauce:
Stir in the rinsed black beans, 1 cup of the tomato sauce, all the spices (cumin, chili powder, red pepper flakes, oregano, salt, pepper). Simmer for a few minutes. Remove from heat and stir in 1 cup of the shredded cheese until melted.

Assemble the Enchiladas:
Preheat your oven to 350°F (175°C). Spread a thin layer of the remaining tomato sauce on the bottom of a 9×13-inch baking dish. Warm the tortillas to make them pliable. Spoon the turkey filling down the center of each tortilla, roll it up tightly, and place it seam-side down in the dish.

Bake and Serve:
Pour the rest of the tomato sauce over the enchiladas and sprinkle with the remaining 1½ cups of shredded cheese. Bake for 20-25 minutes, until the sauce is bubbly and the cheese is melted. Let rest for a few minutes, then top with cilantro and sour cream if desired.