1. Preheat oven to 375º. Sift together sugar, flour, and salt in a bowl. Combine lemon juice, vanilla extract, rum, and orange extract.
2. 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.
3. 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.
4. Spoon batter into an ungreased 10-inch angel food pan with feet.
5. 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.
6. Spread Lemon Curd Filling between layers, leaving a 1/2-inch border. Cover and chill 1 hour.
7. Spread Cream Cheese Frosting on top and sides of cake. Garnish, if desired.