Heat oven to 350°F. Grease bottom of 13 x 9 x 2-inch cake pan. Dust lightly with flour; tap out the excess flour.
Prepare cake mix according to package directions, but decrease the water by 1/4 cup. Add the rum extract. Mix the batter according to the package directions. Stir in 1 cup of the cherry filling and 1/4 cup of the white chocolate, reserving the remaining cherry filling and white chocolate. Pour the batter into the prepared pan.
Bake in 350°F oven 35 minutes or until wooden pick inserted in center comes out clean.
Cool the cake in the pan on a wire rack for 15 minutes. Invert the pan onto the rack; remove the pan. Invert the cake, right side up. Cool completely.
Place cake on serving tray. Frost top and sides. Sprinkle with remaining white chocolate. Top with remaining cherry filling.