Preheat oven to 350°.
Coat an 8-inch square baking pan with cooking spray. Drizzle caramel over bottom of pan. (Caramel will not completely cover bottom of pan.) Arrange apple slices over caramel, overlapping slices slightly.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, sugar, wheat germ, cinnamon, and salt in a large bowl, stirring with a whisk. Combine buttermilk and baking soda in a medium bowl, stirring with a whisk. Stir in applesauce and remaining ingredients. Add buttermilk mixture to flour mixture; stir just until blended. Pour batter over apple slices in prepared pan. Bake at 350° for 35 minutes or until a wooden pick inserted in center of cake comes out clean. Cool 10 minutes in pan on a wire rack. Place a plate upside down on top of cake; invert onto plate. Serve warm.