• Grease a 9x13 pan and line it with parchment paper.
• In a medium bowl, whisk together the 2 cups oat flour, ½ cup almond flour, 2 teaspoons baking powder, 1 teaspoon baking soda, 1 teaspoon fine sea salt, 2 teaspoons ground cinnamon, ¾ teaspoon ground ginger, and ½ teaspoon ground nutmeg.
• In a large bowl whisk together the 1 15-ounce can pure pumpkin puree, 3 large eggs 1 cup oil, ¾ cup granulated sugar, ¾ cup brown sugar, and 3 tablespoons maple syrup until combined. Add the dry ingredients and stir until completely combined, then whisk it for about 30 seconds.
• Spread the batter evenly in the prepared pan, using an offset spatula to smooth the top. Heat the oven to 350℉ and rest the batter while the oven heats. Bake the cake until set and a tester inserted in the center comes out clean, about 1 hour.
• Cool the cake completely in the pan, then cover it and place it in the fridge to chill while you make the frosting.

Make the Frosting

• In a large bowl or bowl of a stand mixer, use a hand mixer or stand mixer on low speed to cream the 8 ounces cream cheese, and 8 tablespoons unsalted butter, together until smooth, and creamy, about 3 minutes.
• Gradually sift in the 4 cups confectioners’ sugar and mix on low until combined

Assemble

• Dollop the frosting over the bars and use an offset spatula to spread it evenly over the entire surface.* Bars will slice best if chilled; place the pan in the refrigerator for 1 hour before slicing. Slice the bars and serve. Bars will keep for several days stored in the refrigerator in an airtight container.