Since this cake is small, use the same recipes to make 4-layer sheet cakes if you need more servings.
For each tier, trim tops of cakes to desired height (see below). Cut each in half horizontally to make 4 layers. Set 1 on a foam-board round; spread top with raspberry buttercream (see amounts, below). Add another layer and frost; repeat until all layers have been added. After adding final layer, smoothly frost top and sides. Refrigerate until firm, about 1 hour.
Roll out fondant following package directions (see amounts, below), and smooth over cake. Cut away excess at the bottom using a pizza cutter (clean fondant can be combined and rerolled). Do not refrigerate finished cake.
To assemble, insert 4 dowels in bottom tier and 3 in middle tier, 2 inches from edge and evenly spaced. Stack tiers on cake stand. Adhere white royal icing Xs and Os to sides of cakes using a bit of leftover royal icing. Serve each cake slice with royal icing Xs and Os.
Tier heights: 9-inch tier: trim each cake to 1 1/2 inches high; finished tier height, 4 1/2 inches. 7-inch: trim each to 1 1/2 inches; finished height, 4 1/2 inches. 5-inch: trim each to 1 inch; finished height, 3 1/2 inches.
Buttercream and fondant amounts: 9-inch tier: 1 1/2 cups buttercream between layers, 1 1/2 cups buttercream for outside (6 cups total), 2 1/4 pounds fondant. 7-inch: 1 cup buttercream between layers, 1 cup for outside (2 1/2 cups total), 1 3/4 pounds fondant. 5-inch: 1/3 cup buttercream between layers, 1/2 cup for outside (1 1/2 cups total), 1 1/4 pounds fondant.