Melt 3 tablespoons margarine in a 10-inch ovenproof skillet over medium-low heat. Add 3/4 cup brown sugar and apple juice, and cook 2 minutes or until sugar melts, stirring constantly. Remove from heat.
Sprinkle sliced almonds over brown sugar mixture. Arrange the peach slices spoke-fashion on top of the almonds, working from the center of the skillet to the edge.
Cream 3 tablespoons margarine and 3/4 cup brown sugar at medium speed of a mixer for 4 minutes. Add egg and vanilla; beat well. Combine flour and next 4 ingredients (flour through salt); stir well. Add flour mixture to creamed mixture alternately with buttermilk, beginning and ending with flour mixture; mix well after each addition.
Spoon batter evenly over peaches. Bake at 350° for 45 minutes or until a wooden pick inserted in center comes out clean. Let cool in pan 5 minutes; invert cake onto a serving plate.