Grease a bundt pan or a 9-inch round cake pan and line it with parchment paper.
Sift together the 1 cup oat flour, 3 tablespoons cornstarch, ⅛ teaspoon baking soda, and ⅛ teaspoon fine sea salt into a medium bowl.
In a large bowl or the bowl of an electric mixer, use a mixer to beat the 9 tablespoons unsalted butter and 4 ounces cream cheese on medium speed until creamy and smooth, about 30 seconds. Gradually add 1 ½ cups sugar of sugar and beat until light and fluffy, about 5 minutes, stopping the mixer occasionally to scrape down the sides of the bowl. Increase the speed to medium-high and add the 3 large eggs one at a time, beating well after each addition, then beat in the 1 teaspoon pure vanilla extract, 2 tablespoons fresh lemon juice, and the zest of 1 lemon.
Reduce the speed to low and gradually add in the flour mixture, beating well until the batter is very smooth and thick,
Spoon the batter into the prepared pan. Preheat the oven to 325℉ and rest the batter.
Place in the oven and bake until the cake is golden and a toothpick inserted into the center comes out clean, about 70 to 75 minutes. Transfer the pan to a wire rack and let the cake cool in the pan for 15 minutes, then gently turn it out onto a wire rack to cool completely.
When the cake is fully cooled, drizzle it with lemon glaze if using, dust with sifted powdered sugar, or enjoy plain!
Notes
Room temperature butter and cream cheese! The best part about this cake is the fluffy base of creamed butter and creamed cheese - this is what gives it that gorgeous cloud-like crumb. Let the butter and cream cheese sit out for up to an hour before starting to make the batter.
Make with gluten-free all-purpose flour. I firmly believe the light and fluffy texture of this cake is greatly aided by the oat flour + cornstarch combo. However, a gluten-free flour mix, like my homemade gluten free flour blend, will also give good results.
Dairy free option. This cake is easy to turn dairy-free! Swap the butter for non-dairy butter and the cream cheese for non-dairy cream cheese or yogurt. Swap 1 cup + 2 tablespoons of flour blend for the oat flour + cornstarch.
Make a lemon soak for the top. In a small pot, whisk together 3 tablespoons of fresh lemon juice and ¼ cup of granulated sugar, then heat over low heat until the sugar dissolves. When the cake is cooled, drizzle the sugar-juice mixture over the top and let it run down the sides and soak in.
Try another citrus. For an orange version of this cake use orange juice and zest. Make a lime cake with lime juice and zest.