Preheat the oven: preheat the oven to 180°C / 350-375°F / Gas Mark 4-5.
Enchilada filling: add the drained tuna, diced red onion, black beans and corn kernels to a large mixing bowl.
Seasoning: then sprinkle in the garlic powder, onion powder, ground paprika, salt and pepper. Stir to gently consistently combine.
Fill and roll: now working one tortilla at a time, place it in the center of a clean and dry cutting board. Spoon a portion of the tuna mixture into the center of the tortilla and gently roll it to combine. Set it aside and repeat this process to fill all of the tortillas.
Baking dish: spray a large baking dish with olive oil. Then pour a small amount of the enchilada sauce into the bottom of the dish and use a spatula to spread it out slightly. Now transfer all of the rolled enchiladas into the dish, pushing them to the side as needed to fit them all in.
Sauce, extra topping and cheese: now pour the remaining sauce over the top of the enchiladas and spread the leftover filling across the top. Spread this gently out also to form its own layer. Once done sprinkle the cheese over the top.
Oven bake: place the baking dish into the oven (uncovered, middle shelf) and let the enchiladas cook and cheese melt for 15 to 20 minutes.
To serve: use oven mitts to remove the cooked enchiladas from the oven. Place the dish onto a heatproof surface and then garnish with chopped parsley. Portion the enchiladas onto plates in pairs of 2. Serve with Greek yogurt, pickled red onion and your favorite extras.