Stir in the garlic powder, cumin, coriander, chili powder, salt and pepper, and serrano peppers and stir until combined and fragrant, about 1 minute. Add the tomato sauce, diced tomatoes, potatoes, green beans and broth and stir to combine. Bring to a low boil, then reduce heat, cover and let simmer for 45 minutes. Stir in fideo noodles and continue to cook, covered, until noodles are soft, about 15 minutes more. Adjust seasoning as desired.