Preheat the oven to 350 degrees. Spray 2 8-inch round cake pans with cooking spray. Line the bottom of the pans with parchment paper and spray the parchment with cooking spray. Lightly dust the pans with flour and set pans aside.

Combine the flour, sugar, baking soda, baking powder, salt, and spices in a large mixing bowl. Beat with an electric mixer set to low until well mixed.

Add the remaining ingredients and beat on low until combined, then turn mixer to medium and beat 3 to 4 minutes, until smooth. Batter will be very thick.

Divide batter between the prepared pans and smooth the top. Bake 34 to 38 minutes, until a cake tester inserted into the center of the cake layers comes out clean. Cool in pans set on wire racks for 20 minutes, then carefully invert onto the rack to cool completely.

Beat the butter and cream cheese in a medium mixing bowl until smooth. Add the maple flavor, salt, 4 cups powdered sugar, and 1 tablespoon of milk. Beat on low to combine, then turn mixer to medium and beat until frosting is very smooth. Add additional milk or powdered sugar if necessary to achieve a spreadable consistency.

Trim your cake layers if they have domed. Set one cake layer on a cake stand or cardboard cake circle and top with about 3/4 cup of frosting. Top with the second cake layer and frost with remaining frosting. If desired, press chopped walnuts into the sides of the cake. Serve.