Sprinkle chicken with salt, and pierce with a fork. Cover and chill 15 minutes.
Melt butter in a skillet over medium heat; add onion, and sauté 8 minutes or until lightly browned. Remove onion with a slotted spoon, reserving drippings in skillet.
Add chicken to skillet, and cook 7 to 8 minutes on each side or until browned. Stir in onion, 1 1/2 cups boiling water, and next 4 ingredients. Cover, reduce heat to low, and cook 30 minutes or until done. Stir in sour cream; cook just until thoroughly heated (do not boil). Serve over rice.