Ok, I'm not sure exactly how to do this. I found a couple recipes on the blog Marathon Mom that I've come to love and would like to share. And if you make this enchilada-sauce, make sure to use it in the Mexican Lasagna recipe, which is also from her blog http://themarathonmom.com/mexican-lasagna.htm.
1/4 cup oil
2 Tablespoons flour
1/4 cup chili powder
1 (8 ounce) can tomato sauce
1 1/2 cups water
1/2 teaspoon cumin
1/2 teaspoon garlic powder
1/2 teaspoon onion powder
1/2 teaspoon salt
In saucepan, combine oil, flour, and chili powder.
Over low heat, stir constantly until bubbly and thickened. (About five minutes or so.)
Whisk in water.
Add tomato sauce and whisk til well blended.
Add spices and stir.
Cook until thickened, ten minutes or less.
Credits: The Marathon Mom, http://themarathonmom.com/