Bring water to a boil in a dutch oven or large pot; cook chicken breasts in boiling water over medium-high heat until chicken is no longer pink in the center, about 20 minutes. Remove chicken from pot and shred, reserving cooking liquid.
Stir cream of chicken soup, corn beans, and tomatoes into cooking liquid. Add shredded chicken; season with cumin, chili powder, and garlic powder and continue simmering.
Melt butter in a skillet over medium heat; cook and stir onion until lightly browned, about 15 minutes. Stir onion into soup and season with salt and black pepper.