Set oven rack in middle position. Heat oven to 350 degrees. Spray two 9-inch round cake pans with nonstick cooking spray; line the bottoms with parchment or waxed paper rounds. Spray the paper rounds, dust the pans with flour, and invert pans and rap sharply to remove excess flour. Or place 24 cupcake liners in a muffin pan and set aside.

Pour milk, egg whites, and extracts into 2-cup glass measure, and mix with fork until blended.

Mix cake flour, sugar, baking powder, and salt in bowl of electric mixer at slow speed. Add butter; continue beating at slow speed until mixture resembles moist crumbs.

Add all but 1/2 cup of milk mixture to crumbs and beat at medium speed for 1 1/2 minutes. Add remaining 1/2 cup of milk mixture and beat 30 seconds more. Stop mixer and scrape sides. Mix at medium speed 20 seconds longer.

Divide batter evenly between two prepared cake pans; using rubber spatula, spread batter to pan walls and smooth tops. Arrange pans at least 3 inches from the oven walls and 3 inches apart. Bake until thin skewer or toothpick inserted in the center comes out clean, 23 to 25 minutes. If making cupcakes, bake for 18-19 minutes or toothpick inserted in the center comes out clean. Remove and allow to cool for a few minutes before transferring to a cooling rack.

Let cakes rest in pans for 3 minutes. Loosen from sides of pans with a knife, if necessary, and invert onto wire racks. Reinvert onto additional wire racks. Let cool completely, about 1 1/2 hours before you frost.

Make the Swiss Meringue Buttercream and set aside.

Brush the crumbs off the cake and place one cake on serving platter that has been lined with pieces of waxed paper to keep the platter clean. Spread the lemon curd on the cake leaving a 1/2-inch border so the jam doesn't seep through the frosting and then top with butter cream on the cake. Add the remaining cake layer on top and gently press.

Generously frost the cake on the sides and the top. With the reserved buttercream, put in a piping bag and with a star tip decorate the cake. Decorate with candied lemon slices.

Remove the waxed paper and serve the cake.

Candied Lemons

Add water and sugar to small saucepan and over high heat bring to a boil and cook until the sugar is dissolved, about 2 minutes. Lower heat to low and add lemon slices and cook for 45 minutes. Remove and drain on a wire rack overnight. Dredge lemon slices in sugar. Lemon slices will keep for several days.