1. Heat oven to 350 degrees F degrees. Butter two 9 x 2-inch-round cake pans with straight sides. Dust with flour; tap out excess flour.
2. Mix together flour, baking powder and salt in large bowl.
3. Beat butter at medium speed in large bowl until light and fluffy. Gradually beat in the sugar until very light and fluffy. Beat in the egg yolks just until blended; do not overbeat. Beat in vanilla.
4. Sift half the flour mixture over butter mixture; lightly stir in. Stir in half of milk. Repeat with the remaining flour mixture and milk.
5. Beat the egg whites in a medium-size bowl with clean beaters until soft peaks form. Stir a little of the beaten whites into the batter to lighten. Gently fold in the remaining whites. Divide the batter equally between the prepared pans.
6. Bake in 350 degrees F oven for 20 to 25 minutes or until the top is lightly browned and a wooden pick inserted in the center comes out clean with no crumbs attached. Transfer the cake pans to wire racks to cool. Remove the cakes from the pans. Sandwich the layers together with lemon curd. Dust the top with confectioners sugar if desired.