Butter 2 (9-inch) cake pans with 1 tablespoon of butter. Line with parchment paper and butter the paper with 1 tablespoon of butter. Set aside.
In a large bowl, with a mixer, cream the remaining 1 1/2 sticks of butter with the sugar. Add the yolks 1 at a time, beating well after the addition of each.
Into a medium bowl, sift the flour, baking powder and salt. Alternating with the milk, add to the egg mixture, beating.
In a bowl, beat the egg whites until stiff peaks form. Fold with the vanilla into the batter. Pour into the prepared cake pans and bake until golden and a tester inserted into the middle comes out clean, about 30 minutes.
Remove from the oven and cool on a wire rack. Turn out the cakes, remove the paper, and let cool completely.
To ice the cake: Place 1 cake layer on a cake plate or stand. Spread the icing on top of the layer, spreading out to the edge of the cake. Top with the second cake layer. Ice the top and sides of the cake with the icing. Decorate with toasted, sliced almonds.
Yield:frosting and filling for 2 (9-inch) cakes
Cream the shortening and butter together in the bowl of an electric mixer. Add the lemon juice and salt. Gradually add the sugar, 1 cup at a time. Add the meringue powder - the mixture will appear dry. Add the milk and beat until light and fluffy, about 5 to 8 minutes. Keep bowl covered with a damp cloth or plastic wrap.