Preheat the oven to 400ºF (200ºC). Grease the sides of an 8-inch (20-cm) springform pan with butter. Flour lightly. Line the bottom with a sheet of parchment (cut it to fit if not using precut round sheets).

Add the egg whites and salt to a medium bowl. Beat on medium-high until stiff peaks form. Set aside.

Add the butter and sugar to a clean, medium bowl. Beat until fluffy and well mixed.

Add the flour and almond extract. Beat until just combined. The batter will be very stiff, and more like cookie dough. Stir in a third of the beaten egg whites to loosen up the batter.

Gently fold in the remaining egg whites.

Spread the batter into the prepared pan. Arrange the peach slices on the top in a swirl pattern.

Bake 32 to 35 minutes, until puffed, golden, and cake springs back when tapped in the center. Remove from oven, and let cool completely on a wire rack before removing from the tin. Dust with confectioners’ sugar before serving, if desired.