1 3/4 Cups Maple Sugar
1 Cup + 2 Tbsp Cake Flour
1/4 tsp Salt
12 Large Egg Whites, at room temperature
1 1/2 tsp Cream of Tartar
1 1/2 tsp Pure Vanilla Extract
Optional - whipped cream and berries
Adjust oven rack to the lower middle position and preheat oven to 325F.
In a food processor or blender, pulse the maple sugar until fine and powdery. Remove 1 cup and set aside. Add the cake flour and salt to the maple sugar in the processor. Pulse 5-10 times until the maple sugar/flour/salt mixture is aerated and light.
Whip egg whites and cream of tartar together on medium-low until foamy (about 1 minute) in a stand mixer fitted with a whisk attachment, or a large bowl with a hand mixer. Switch to medium-high and slowly add the reserved cup of maple sugar. Whip until soft peaks form, about 5-6 minutes. Add the vanilla extract and beat until just incorporated.
In 3 additions, slowly sift the flour mixture into the egg white mixture, gently folding with a rubber spatula after each addition. (To avoid deflating the cake or making a dense cake don't add all the flour at once.) Sift and slowly fold in several additions.
Pour and spread batter into an ungreased 9 or 10 inch tube pan. Shimmy the pan on the counter to smooth the surface.
Bake at 325F until a toothpick inserted comes out clean, about 40-45 minutes. Rotate the pan halfway through the baking.
Remove from the oven, then cool the cake completely, upside down on a wire rack in the pan, about 3 hours. Once cooled, run a thin knife around the edges and gently tap the pan on the counter until the cake releases.
Top with whipped cream and berries if you would like, and enjoy!