To prepare filling, combine first 5 ingredients in a large saucepan, and bring to a boil. Cover, reduce heat, and simmer 35 minutes or until the liquid is nearly absorbed. Place apple mixture in a food processor; pulse 8 to 9 times or until the consistency of a chunky puree. Set aside.
Preheat oven to 350°.
To prepare cake, beat shortening and 1 cup brown sugar at medium speed of a mixer until light and fluffy. Add molasses, 1 teaspoon vanilla, and eggs; beat well.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 5 ingredients (flour through salt) in a bowl. Add flour mixture to sugar mixture alternately with buttermilk, beginning and ending with flour mixture.
Pour batter into a 12-cup Bundt pan coated with cooking spray. Bake at 350° for 40 minutes or until a wooden pick inserted in center comes out clean. Cool 10 minutes in pan. Remove from pan; cool completely on a wire rack.
Split cake into thirds horizontally using a serrated knife. Place bottom layer, cut side up, on a serving platter; spread with half of filling. Top with middle cake layer. Spread cake with remaining filling; top with remaining cake layer. Sift powdered sugar over top of cake.