Vanilla Bean Angel Food Cake

Your sense of touch will tell you when the vanilla seeds are thoroughly mixed with sugar. In addition, you will know that the cake is ready to bake when you tap on the surface and it springs. If desired, serve with fresh berries or whipped cream without fat.
Preheat the oven to 325 degrees.Pour 3/4 cup sugar into a small bowl. Peel the vanilla beans from the seeds and add them to the sugar; discard the seeds. Rub vanilla seeds with sugar with your fingers until smooth.Lightly spoon the flour into a dry measuring cup; smooth with a knife. Combine the flour and sugar mixture, stirring with a whisk.Beat the egg whites with a mixer on high speed until frothy. Add the tartar and salt; beat until soft peaks form. Add the remaining 3/4 cup sugar, 2 tablespoons at a time, whisking until stiff peaks form. Whisk in the juice. Sift the flour mixture over the egg white mixture, 1/4 cup at a time; add the flour after each addition.Spoon the batter into an ungreased 10-inch tube pan, spreading evenly. Cut the dough with a knife so that no air pockets form. Bake at 325 ° C for 50 minutes or until the cake begins to spring with a light touch. Turn the pan upside down; cool completely. Loosen the cake from the sides of the mold using a narrow metal spatula. Flip the pie onto a plate.