Coat a 10-inch tube pan with cooking spray.
Place granulated sugar, brown sugar, and 1/2 cup butter in a large bowl; beat with a mixer at medium speed for 3-5 minutes or until well blended.
Add eggs, 1 at a time, beating well after each addition.
Stir in pumpkin and vanilla.
Combine flour, cinnamon, baking powder, baking soda, and salt in a bowl, stirring well with a whisk.
Add flour mixture and buttermilk alternately to sugar mixture, beginning and ending with flour mixture.
Spoon batter into prepared pan.
Bake at 350° for 55 minutes or until a wooden pick inserted in center comes out mostly clean (a few crumbs are great!). Cool in pan for 10 minutes on a wire rack. Remove from pan, and cool completely on wire rack.
Drizzle cake with glaze. If you drizzle while the cake is warm the glaze will soak into the cake more. If you drizzle when the cake is cool, the glaze will appear thicker.