In a small bowl, combine flour, chili powder, garlic powder, cumin, oregano, salt and pepper.
Heat oil in a saucepan over MED heat until warm, then add the flour and spices mixture and whisk well. Cook for 1-2 minutes, whisking occasionally.
Whisk in tomato paste. Slowly pour in chicken broth, whisking as you pour to eliminate any lumps.
Increase heat a bit to bring to a high simmer, then reduce heat to MED LOW to simmer the sauce. Simmer, whisking often, for 5-10 minutes, until the sauce is thickened some and the sauce coats the back of a wooden spoon.
Turn off heat, and whisk in the vinegar (if using), then taste and add more salt and pepper if needed.
Use immediately, or cool completely and store.
