Sprinkle chicken breasts with salt. Dip in flour, shaking off excess. Heat large skillet over med-high heat until hot. Add oil; heat until hot. Cook chicken in batches 8-10 minutes or until golden, turning once. Remove chicken.
Cook onion and garlic in same skillet over medium heat 5 minutes or until browned. Stir in salsa verde, water and cilantro. Return chicken to skillet. Simmer 10-15 minutes or until chicken is no longer pink in center. Remove from heat; place chicken on platter.
Whisk sour cream into onion mixture (do not boil); pour over chicken.