Prep: 30 min.; Bake: 34 min.; Cool: 1 hr., 30 min.; Chill: 1 hr. An angel food cake pan looks similar to a traditional tube pan, but it has a removable bottom and three or four metal "feet" attached to the top rim. The feet allow the pan to be inverted while cooling, which yields a light and fluffy cake texture. Be sure to let the cake cool completely (1 1/2 hours) before cutting horizontally into three equal rounds.
Preheat oven to 375º. Sift together sugar, flour, and salt in a bowl. Combine lemon juice, vanilla extract, rum, and orange extract.
Beat egg whites and cream of tartar at high speed with a heavy-duty electric stand mixer until stiff peaks form; gently transfer egg white mixture to a large bowl.
Gradually fold in sugar mixture with a large spatula, 1/3 cup at a time, folding just until blended after each addition. Fold in lemon juice mixture.
Spoon batter into an ungreased 10-inch angel food pan with feet.
Bake at 375º for 34 to 38 minutes or until a long wooden pick inserted in center comes out clean. Invert cake, and let cool in pan 1 hour. Remove cake from pan to a wire rack, and let cool completely (about 30 minutes). Cut cake horizontally into 3 equal rounds.
Spread Lemon Curd Filling between layers, leaving a 1/2-inch border. Cover and chill 1 hour.
Spread Cream Cheese Frosting on top and sides of cake. Garnish, if desired.