Heat oil in a skillet over medium-high heat. Stir in flour and chili powder, reduce heat to medium, and cook until lightly brown, stirring constantly to prevent burning flour.

Gradually stir in tomato sauce, water, cumin, garlic powder, and onion salt into the flour and chili powder until smooth, and continue cooking over medium heat approximately 10 minutes, or until thickened slightly. Season to taste with salt.