1-Preheat oven to 325°F (163°C) with the rack in the lower middle position.

2-Pulse granulated sugar in a food processor until superfine; remove 1 cup and set aside.

3-Add cake flour and salt to the remaining sugar in the processor; pulse 5 10 times to aerate.

4-In a large bowl, whip egg whites and cream of tartar on medium-low speed until foamy (about 1 minute).

5-Increase speed to medium-high, gradually add the reserved 1 cup superfine sugar, and whip until soft peaks form (about 5 6 minutes). Mix in vanilla briefly.

6-Sift the flour mixture over the egg whites in three additions, folding gently after each to preserve volume.

7-Pour batter into an ungreased 9 or 10-inch tube pan; smooth the top by shimmying the pan.

8-Bake 40 45 minutes, rotating the pan halfway, until a toothpick inserted comes out clean.

9-Cool the cake completely upside down on a wire rack for about 3 hours.

10-Run a thin knife around the edges and tap the pan to release the cake.

11-Dust with confectioners’ sugar (optional), slice with a serrated knife, and serve with whipped cream and berries (optional).

12-Store leftovers refrigerated for up to 5 days.