Preheat the oven to 190°C (375°F). Grease a large rectangular casserole dish or 9x13-inch pan.
Melt the butter in a medium saucepan over medium heat. Stir in the flour. Saute the beef and add the two bottles of salsa. Stir in the taco sauce. Bring to a boil, then reduce the heat to a simmer while preparing the enchiladas.
Lay the tortillas out on a clean, flat surface. Reserve 1 cup of the cheese. Distribute the remaining cheese and the chopped spinach between each tortilla.
Spread ⅔ cup of the enchilada sauce in the bottom of the prepared baking pan. Roll up the tortillas and place side by side, seam side down, in the pan. Spread the remaining sauce over the enchiladas. Sprinkle with the reserved cheese.
Bake in the oven using the top and bottom heat + fan function for 15 to 20 minutes or until the cheese is completely melted.
Sprinkle the enchiladas with the chopped cilantro, if desired, and serve warm.