Preheat the oven to 350℉ and grease 2 8-inch pans and line them with a circle of parchment paper.
In a large bowl, whisk together the 4 large eggs, 1 can pure pumpkin puree, 1 cup granulated sugar, ¾ cup light or dark brown sugar, and 1 cup vegetable or canola oil until smooth.
In a medium bowl, whisk together the 1 ¾ cups oat flour, ½ cup almond flour, 3 teaspoons baking powder, 1 teaspoon ground cinnamon, ½ teaspoon ground ginger, ½ teaspoon ground nutmeg, and ½ teaspoon fine sea salt. Fold the dry ingredients into the wet ingredients mix, and stir until a smooth batter forms with no pockets of flour remaining.
Pour batter into the prepared pans, let the batter rest for 20 minutes, then place in the oven and bake for 30-35 minutes, until a tester inserted in in the centers comes out clean.
Place the pans on a wire rack and cool for 10 minutes in the pan, then turn out to cool completely.
Make frosting: Beat the ½ cup unsalted butter and 1 8-ounce brick regular cream cheese until fluffy, then beat the 3 cups powdered sugar and 1 teaspoon pure vanilla extract until smooth. Fill and frost the cooled cake.
Notes
Room temperature cream cheese and butter. I can't stress how important this is so I'm mentioning it again! Softened, room temperature cream cheese and butter - think, your finger being easily able to press into both - are vital to making the smoothest and fluffiest frosting that's totally lump-free.
Use gluten free flour. If you don't have oat or almond flour, simply use your favorite gluten free flour blend - mine is my homemade gluten free flour blend - in place of the two flours for great results.
Try butternut squash. For a twist on pumpkin that's still super fall-appropriate, swap 2 cups of butternut squash puree for the pumpkin puree.
Skip the baking soda. Lots of pumpkin recipes call for baking soda, but I don't like the slightly salty aftertaste it can leave. Instead, three teaspoons of baking powder add the right amount of lift for nicely fluffy cake layers.