Brown flour in oven until golden brown. (Place in baking pan. Cook at 400 degrees for about 30 minutes.) Turn oven temperature down to 200 degrees.
In skillet, combine oil, browned flour, chili powder, cumin, garlic and salt. Blend well.
Over low heat, Gradually add water stirring constantly. If flour begins to lump, remove from heat immediately and stir until lumps are gone. Then return to heat and continue adding water a little at a time.
Simmer gently, stirring occasionally, for 1 hour.
While the sauce is cooking: In a small skillet, heat 1/2 inch of oil to hot but not smoking. One at a time immerse tortilla in hot oil for about 30 seconds, turning once. Remove at once a tortilla must remain pliable and not get crisp. Continue until all tortillas have been cooked and set aside in a warm place.
Place 3 Tbsp. cheese and 1 tsp. onion in center of each tortilla. Roll up the tortilla and place in a shallow baking pan seam side down. (Pan should be large enough for 10 enchiladas to fit snugly in a single layer.)
Over the rolled up enchiladas, pour the sauce. Be careful as the sauce is very hot. Sprinkle a little cheese over the sauce.
Place the pan in the 200 degree oven and turn the oven off. Leave in the closed oven for 20 minutes. If you leave the oven on the cheese melts too much and enchiladas lose their shape. Serve immediately.
NOTE: I like to fry the onion a little to soften it as I don't care for crunchy onion in my enchiladas.