Melt butter in a lightly greased 13- x 9-inch baking dish in a 425° oven.
Sprinkle chicken with salt and pepper. Dip chicken in 1/2 cup buttermilk, and dredge in flour. Arrange chicken, breast side down, in dish.
Bake at 425° for 25 minutes. Turn chicken, and bake 10 more minutes. Stir together remaining 1 cup buttermilk and soup; pour over chicken, and bake 10 more minutes, shielding with aluminum foil to prevent excessive browning, if necessary. Serve over rice.