Sprinkle pecans evenly into 3 generously buttered 9-inch round cake pans; shake to coat bottoms and sides of pans. Spoon Pecan Pie Cake Batter evenly into prepared pans.
Bake at 350° for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes. Invert layers onto wax paper-lined wire racks. Brush tops and sides of layers evenly with corn syrup, and cool completely.
Place 1 cake layer, pecan side up, on a serving plate. Spread top with half of Pecan Pie Filling. Place second layer, pecan side up, on top; spread top of cake layer with remaining filling. Top with remaining layer, pecan side up. Garnish slices, if desired.