Heat the oven to 350 degrees. Coat a 9x5-inch loaf pan with nonstick cooking spray. Line with parchment paper and coat the paper with cooking spray. To prepare the first cake, combine one cake mix with 2/3 cup of the sour cream, 1/4 cup of the oil and 2 of the eggs in large bowl. Beat on low speed for 30 seconds or until combined. Increase the speed to medium and beat for 2 minutes. At low speed, beat in the food coloring to reach desired color. Beat in the raspberry extract. Spoon the batter into the pan. Bake for 50 to 60 minutes or until a wooden pick inserted in the center comes out clean. Cool in the pan on a wire rack for 10 minutes. Remove from the pan and cool completely. Using a 2 to 2 1/2-inch heart-shaped cookie cutter (the height of pound cake slice), cut the cake into 1/2- to 3/4- inch thick slices (no thicker than the heart-shaped cutter). Cut the heart-shapes out of the pound cake slices and place on the parchment paper-lined baking sheet. Freeze for 30 to 60 minutes or until frozen. (Reserve the remaining cake pieces for another use.) Meanwhile to prepare the second cake, heat the oven to 350 degrees and prepare the same cooled 9x5-inch loaf pan as directed above. Combine the remaining cake mix, 2/3 cup sour cream, 1/4 cup oil and 2 eggs in a large bowl. Beat on low speed for 30 seconds or until combined. Increase speed to medium and beat for 2 minutes. Do not add food coloring or flavor extract to this batter. Pour enough batter into the prepared loaf pan to just cover the bottom. Stack the frozen heart-shaped cake pieces down the center of the loaf pan, fitting snuggly. Pour the remaining batter into the pan to fill the sides and cover to the top of the heart shapes. Bake for 55 to 60 minutes or until a wooden pick inserted near the center comes out clean. Cool in the pan on a wire rack for 10 minutes. Remove from the pan and cool completely. Frost the top of the cake and garnish with sprinkles if desired.