In a large bowl, cream shortening and sugar until light and fluffy. Beat in egg whites and cherry juice. Combine the flour, baking powder and salt; add to the creamed mixture alternately with the milk, beating well after each addition. Stir in cherries and nuts.
Place the batter in two greased and floured 9-in. round baking pans. Bake at 350° for 30-35 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
For frosting, combine the sugar, egg whites, water, corn syrup and cream of tartar in a heavy saucepan over low heat or double boiler over simmering water. With a portable mixer, beat on low speed for 1 minute. Continue beating on low over low heat until frosting reaches 160°, about 8-10 minutes.
Pour into the bowl of a heavy-duty stand mixer; add vanilla. Beat on high until stiff peaks form, about 7 minutes. Spread between the layers and over the top and sides of cake. Garnish with cherries if desired.