• Preheat oven to 350 degrees. Coat a 9” angel food cake pan, springform pan, or bundt pan with cooking spray.
• Using an electric mixer or in a large bowl using a hand mixer, combine cake mix, flour, pudding, pumpkin, water, and canola oil.
• Add egg whites and egg and mix well.
• Stir in vanilla, pumpkin spice, and cinnamon.
• Mix on high for at least one minute. Scrape down sides and mix again.
• Pour ½ of the batter evenly into pan. Sprinkle with ¼ cup rolled oats. Pour remaining batter and spread evenly. Sprinkle with remaining ¼ cup rolled oats. Shake the pan on work surface after filling the batter to even out the batter.
• Bake for at least 1 hour until a toothpick comes out mostly clean. It might take an extra 5 to 10 minutes depending on your oven. Let rest at least 15 minutes before removing from pan.

To make the glaze:

• Place the sugar, sugar substitute, buttermilk, light butter, baking soda, and vanilla in a small saucepan and heat over medium heat.
• Bring to a boil stirring constantly.
• The glaze will foam up and thicken as the sugar dissolves and butter melts, about 2-3 minutes.
• Using a fork, poke 12 holes all over warm cake and spoon the hot buttermilk glaze all over cake.