1 1/2tablespoonsorange liqueuror additional orange juice
Preheat your oven to 300 degrees F. Generously coat a 9-inch round cake pan with nonstick spray and line the bottom with parchment paper.
In a medium bowl, beat the egg whites with an electric mixer until the whites hold stiff peaks (do not over beat or the whites will separate). Set aside.
To a large mixing bowl (or the bowl of a stand mixer fitted with the paddle attachment) add the sugar. Zest the orange right over the top. With your fingers, rub to combine until the sugar is fragrant and feels lightly moist. Juice the zested orange and set aside (you’ll need juice for both the cake and the glaze).
Add the butter to the bowl with the sugar. Beat until it looks pale and fluffy (if you are using the same beaters you did for the egg whites, no need to wash them). This will take 1 to 2 full minutes. Stop to scrape down the bowl as needed.
Beat in the egg yolks one at a time, ensuring each yolk is completely incorporated before adding the next.
Add the yogurt, orange liqueur, almond extract, and 1/4 cup of the reserved orange juice. Mix until smooth, stopping to scrape down the bowl as needed. The mixture will look curdled but will be absolutely fine.
Sprinkle the salt over the top, then sprinkle on the almond flour and cornmeal. With the mixer on low speed, blend just until the dry ingredients disappear.
Add a small amount of the egg whites to the bowl with the batter. With a rubber spatula, gently fold to combine (this lightens the batter initially). Once they are mostly incorporated, add the remaining egg whites and fold in gently. Stop as soon as you no longer see white streaks.
With a large spoon, carefully scoop the batter into the cake pan in big dollops (try to keep the batter as light as possible). With an offset spatula or the back of a spoon, gently smooth the top.
Bake the polenta cake for 38 to 42 minutes, until a toothpick inserted in the center comes out clean and the sides of the cake have begun to pull away from the sides of the pan.
Place the cake on a cooling rack and let cool for 5 minutes. Run a knife around the edge of the cake to loosen it, then invert it onto a serving plate. Let cool completely before glazing.
While the cake cools, prepare the glaze: in a medium bowl, whisk together the powdered sugar, orange liqueur, and orange juice until smooth. The glaze should be thick but spreadable. Add more powdered sugar or orange juice/liqueur as needed to achieve the right consistency.
Once the cake is cool, spoon the glaze into the center. With the back of your spoon or an offset spatula, spread it over the top of the cake (leave the outsides bare). Let sit for 5 to 10 minutes to allow the glaze to set. Slice and enjoy!
*For best results, I HIGHLY recommend weighing the almond flour in this recipe, as the way you pack the cup can cause significant variation in amount (even bags of almond flour disagree on what "1 cup" weighs). An inexpensive kitchen scale like this one is a wonderful, important tool and one you'll use far more often than you think!
TO STORE. Store the cake in the refrigerator for up to 1 week. We love this cake even better on day 2, because the almond flour makes it even more moist.