Cut end off chili and clean out all seeds. Cover with water and bring to a boil. Once cooled put 1/3 at a time in blender, place pulp in colander. Place over large pot and run water through until colorless. Bring liquid to boil.
Blend, half at a time, seasoning flour and water in blender, add to sauce. Stir constantly until thick. Use over beef or Cheddar enchiladas.