Heat oil over medium heat in a medium sauce pan. Add onion, celery and bell pepper. Turn down the heat and cook until soft.
3 tbsp vegetable oil, 1 cup onion, 1/2 cup celery, ½ cup bell pepper
Add Tex-Mex spice blend and flour, mixing well. Simmer until flour starts to brown.
2 tbsp Tex-Mex spice blend, 3 tbsp flour
Add chicken broth, tomato sauce, and whole tomatoes. Break up whole tomatoes into the sauce.
2 cups chicken broth, 8 ounces tomato sauce, 16 ounces whole tomatoes
Turn heat to low and simmer for 25-30 minutes. Add water as necessary.
1/2 cup water