Pre-heat oven to 350 degrees. In a stand mixer, cream the butter, oil, and sugar. Add eggs, lemon juice, and vanilla. Mix again. Add dry ingredients and buttermilk. Mix until fully incorporated. Scoop batter over the fruit and caramel, smooth the top and bake for about 45 minutes or until browned and toothpick comes out clean when inserted. Cool on a wire rack. Invert the cake onto a plate. Serve.