Preheat oven to 350°F (175°C). Grease a 9-inch springform pan and line the bottom with parchment. Whip the egg whites to stiff peaks in a clean bowl, about 3 to 4 minutes.

Cream the butter and sugar until light and fluffy, about 3 minutes. Beat in the egg yolks, vanilla, almond extract, and lemon zest.

Fold the almond flour, baking powder, and salt into the butter mixture until just combined. Gently fold in the whipped egg whites in three additions until no streaks remain.

Pour the batter into the prepared pan and smooth the top. Bake until golden and a toothpick comes out with moist crumbs, 30 to 35 minutes.

Cool in the pan for 10 minutes, then remove the ring and cool completely on a rack. Dust with powdered sugar before serving.