1 (15.25 ounce) box Betty Crocker Yellow Cake mix
1 (3.4 ounce) package instant vanilla pudding mix
1 tablespoon homemade pumpkin pie spice
3/4 cup sour cream
3/4 cup vegetable oil
1/2 cup warm water
4 eggs, lightly beaten
2 teaspoons pure vanilla extract

For the Spiced Buttercream
2 cups (4 sticks) unsalted butter, room temperature
1.5 pounds (about 5 3/4 cups) confectioners' sugar, sifted
1/2 teaspoon homemade pumpkin pie spice
2 teaspoons pure vanilla extract
4 tablespoons heavy cream