There are many ways to decorate a standard 13-by-9 rectangular cake. Think of the cake as a blank canvas, ready to be transformed with a little frosting and a lot of imagination. Ideas can be easy or complicated, depending on your skill level, available time and access to cake-decorating tools. And, in the end, there are few desserts that are as easy to cut and serve as a rectangular cake.
Decorating Cakes with Figures and Words
Themed cakes are often decorated with figurines, gumpaste sculptures or fondant shapes that can be spread across the expanse of a rectangular cake. If this idea seems overwhelming, check a chemist or dollar store for small toys that will fill the bill.
If, on the other hand, you just want a cake that says "Congratulations!" there's no sweeter writing surface than a rectangular cake. You might think that decorating a cake with words is only for those with amazing handwriting and a very steady hand. But you can "cheat" by making the letters on waxed paper first.
Print the words you want to write, then trace them onto a piece of waxed paper. Turn the waxed paper over so that the letters are now backward, and tape it onto a baking tray or a piece of cardboard.
Use a squeeze tube of frosting or a piping bag with a round tip to dispense the frosting onto the letter template. Then, stick the entire thing into the freezer.
Once the letters are frozen, you can clean up any messy edges or mistakes simply by removing them from the waxed paper. Individual letters can be sculpted to perfection by trimming any excess frosting.
Use a craft knife to cut the waxed paper into squares around each letter, then transfer the frozen letters one by one onto your cake. You also might want to try your hand at making flowers or other shapes to embellish the edges of the cake.
Another popular way to decorate cakes is with a photograph. You can buy edible printing systems which include special paper and ink that can be placed on a cake. Many grocery store bakeries and speciality cake bakers have these systems and can print the images for you, for a fee.
A rectangular sheet cake frames a photo nicely, and it's easy to decorate. Cover the cake with a layer of white frosting and smooth it out as much as possible. To apply the edible photo, first trim it to size, then place it in the freezer for up to a minute. In the meantime, spray the top surface of the cake with a fine mist of water. Remove the photo from the freezer, then carefully peel off the backing. Lay it gently on the cake and let it settle for 2-3 minutes onto the wet frosting. For a "frame," add a rim of piped, gumpaste or sugar flowers or a solid line of squeeze tube frosting onto the edges of the photo. You can press candies onto the edge as well.
The simple shape of a rectangular cake belies the extravagant ways it can be transformed. By carving the rectangle into another shape, you can create a sculpted cake your guests will remember for a long time.
Your cake will be easier to carve if you freeze it first. Allow it to cool completely after baking, then place it on a baking tray lined with parchment paper and put it in the freezer for at least 30 minutes. A frozen cake will cut nicely without breaking or making excessive crumbs.
One sculpted cake that's easy to make from a rectangle is a football cake. After freezing the cake, use a bread knife to cut it into a football shape. You can do this freehand or by using a traced template.
Frost the entire cake with a reddish-brown shade of frosting to match the pigskin; chocolate works, too. For the first layer of frosting, it's important to "seal" the cut edge of the cake to prevent crumbs. You can do this while the cake is still frozen. Apply an initial layer of frosting fairly thickly, and use a new knife each time you see crumbs. Allow this initial layer to dry thoroughly before applying the actual decorative frosting.
Once it's football-coloured, use a white squeeze tube of frosting to create the characteristic stripes on either end and the stitching in the middle. This cake works well for a birthday party, tailgate or Super Bowl gathering.