Drain cherries,reserving 1/2 c. juice.Combine reserved cherry juice,cherries,gran sugar and cornstarch in a saucepan.Cook and stir over low heat until thickened.Add vanilla and stir.
Split each cake layer in half horizontally.Crumble one half layer;set aside.
Beat cold whipping cream and conf sugar in a L. bowl with a electric mixer set at high speed until stiff peaks form.Reserve 1 1/2 c. whipping cream for decorative piping.
Place one cake layer on serving plate.Spread with 1 c. whipping cream;top with 1/4 c.cherry topping.Top with second cake layer,1 c. whipping cream and 3/4 c. cherry topping;top with third cake layer.
Frost cake sides with remaining whipped cream;pat gently with reserved cake crumbs.
Spoon reserved 1 1/2 c. whipped cream into pastry bag fitted with star tip;pipe around top and bottom edges of cake.Spoon remaining cherry topping over top of cake.
** If you place bowl and beaters in fridge before being needed..it helps with making the peaks form easier..Also make sure whipping cream is chilled..