orange sponge cake

Ingredients For orange sponge cake

• 6

  egg yolks (reserve whites)
• 1 1/2 c

  sugar
• 1 tsp

  fresh lemon rind, grated
• 1 tsp

  fresh orange rind, grated
• 1 Tbsp

  fresh lemon juice
• 1/3 c

  fresh orange juice
• 1 1/2 c

  flour
• 1 1/2 tsp

  baking powder
• 1/2 tsp

  salt
• 6

  egg whites, at room temp.
• 1/2 tsp

  cream of tartar