Pumpkin Pound Cake

Cake:

• Cooking spray
• 1 tablespoon all-purpose flour
• 1 (15-ounce) can pumpkin
• 3/4 cup granulated sugar
• 3/4 cup packed dark brown sugar
• 1/2 cup butter, softened
• 4 large eggs
• 1 teaspoon vanilla extract
• 3 cups all-purpose flour (about 13 1/2 ounces)
• 1 1/2 teaspoons pumpkin pie spice
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon salt
• 3/4 cup fat-free buttermilk