Mix buttermilk and garlic powder in bowl. Add chicken and let marinate 2 hours or more. Baste and turn often.
Melt butter in a deep skillet and saute onions 10 minutes, stirring frequently.
Meanwhile, mix salt, ginger, curry and cornstarch together in a small bowl and sprinkle over onions, stirring until well blended.
Drain the chicken (reserve the buttermilk) and cook the chicken in the same skillet until lightly browned. Stir in buttermilk. Cover and cook over low heat 1 1/2 hours or until chicken is tender. Baste frequently.