Preheat the oven to 350°F (180°C) and lightly grease a baking dish measuring about 9 x 11 inches (22 × 28 cm) with cooking spray.
Start by preparing the enchilada sauce. Add the diced tomatoes to a blender and blend briefly until smoother in consistency.
Heat the vegetable oil in a saucepan over medium heat. Add the flour and chili powder and immediately whisk to combine. Cook for about 1 minute, whisking continuously.
Gradually add the blended tomatoes and chicken broth, whisking to prevent lumps from forming.
Add the smoked paprika, cumin, garlic powder, onion powder, and oregano.
Let the sauce simmer over medium-low heat for a few minutes, stirring occasionally, until it begins to thicken slightly. It should still remain fairly fluid so the tortillas stay soft during baking. Season with salt and black pepper and set aside.
Heat a nonstick skillet and add the red bell pepper. Cook for about 4–5 minutes, stirring occasionally, until it begins to soften but still retains some texture.
Transfer the shredded chicken, black beans, corn, and bell pepper to a large bowl.
Add the Greek yogurt and about 3.5 oz (100 g) of the enchilada sauce. Mix until the filling is creamy and well combined. Taste and adjust with salt and pepper if needed.
Spread a thin layer of enchilada sauce over the bottom of the baking dish.
Cut the tortillas as needed so they cover the bottom of the dish without leaving large gaps.
Create the first layer using about one-third of the tortillas.
Spread half of the chicken, bean, and corn filling over the tortillas. Add about one-third of the shredded scamorza and a few spoonfuls of enchilada sauce.
Cover with a second layer of tortillas.
Add the remaining filling, another third of the scamorza, and a few more spoonfuls of sauce.
Finish with the final layer of tortillas.
Pour all the remaining enchilada sauce over the top, spreading it evenly and making sure the edges of the tortillas are well covered.
Top with the remaining scamorza.
Cover the baking dish with aluminum foil and bake in the preheated conventional oven at 350°F (180°C) for about 20 minutes.
Remove the foil and continue baking for another 10 minutes, or until the scamorza is fully melted and the sauce begins to gently bubble around the edges.
Remove the casserole from the oven and let it rest for about 10 minutes before slicing. This allows the layers to settle and makes it easier to cut into neat portions.
Serve hot and, if desired, top with a little Greek yogurt or avocado.