Orange Sponge Cake

Ingredients (12)

• 6 large eggs, separated
• 1-1/3 cups cake flour
• 1-1/2 cups sugar, divided
• 1/4 teaspoon salt
• 1/2 cup orange juice
• 3 teaspoons grated orange zest
• 3/4 teaspoon cream of tartar
• GLAZE:
• 1/3 cup butter, cubed
• 2 cups confectioners' sugar
• 3 to 5 teaspoons water
• 1-1/2 teaspoons vanilla extract