Begin by making the sauce. In a small sauce pot, combine the chili powder, flour, and oil. Heat over a medium flame, while stirring, for one to two minutes to toast the spices and flour. Whisk in the water, tomato paste, cumin, garlic powder, and cayenne pepper. Allow the mixture to come to a simmer, at which point it will thicken. Once thick enough to coat a spoon, taste and add salt as needed (1/2 to ¾ tsp). Set the sauce aside.
Toast the tortillas in a dry skillet over medium flame until they are just flecked with brown on each side. The tortillas should be slightly more firm, but still pliable enough to roll. Stack the tortillas on a clean plate as they come out of the skillet.
Prepare a casserole dish by coating with non-stick spray, then spread a layer of enchilada sauce over the bottom (1/2 to 1 cup). Preheat the oven to 350 degrees.
Add about ¼ cup of refried beans to each tortilla, plus a small pinch of shredded cheese. Roll the tortilla tightly around the beans and cheese, then place seam side down in the casserole dish. Continue until all of the tortillas are filled. Pour another ½ to 1 cup enchilada sauce over the rolled enchiladas in the dish, leaving some of the edges exposed so they can become brown and crispy. Top with the remaining shredded cheese.
Bake the casserole in the oven for 25-30 minutes or until the sauce is thick and bubbly around the edges and the center is heated through.
Top with thin slices of avocado and chopped cilantro leaves (or sliced green onions).