1. Preheat oven to 350°. Bake pecans in a single layer in a shallow pan 5 to 7 minutes or until lightly toasted and fragrant, stirring halfway through. Let cool.
2. Meanwhile, beat butter at medium speed with a heavy-duty electric stand mixer until creamy. Gradually add sugar, beating until light and fluffy. Add eggs, 1 at a time, beating just until blended after each addition.
3. Stir together flour, baking soda, and salt; add to butter mixture alternately with buttermilk, beginning and ending with flour mixture. Beat at low speed just until blended after each addition. Stir in vanilla.
4. Divide batter into 2 equal portions (about 3 1/2 cups each); stir cinnamon, allspice, cloves, and pecans into 1 portion. Pour plain batter into 2 greased and floured 9-inch round cake pans (about 1 3/4 cups batter per pan). Pour spiced batter into 2 greased and floured 9-inch round cake pans (about 2 cups batter per pan).
5. Bake at 350° for 18 to 20 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes; remove from pans to wire racks, and cool completely (about 1 hour).
6. Place 1 plain cake layer on a serving plate or cake stand; spread top with 2/3 cup Filling, leaving a 1/4-inch border around edges. Top with a spice cake layer, and spread top with Filling as directed above. Repeat procedure with remaining plain cake layer and Filling. Top with remaining spice cake layer. Prepare White Icing; spread icing over top and sides of cake.