There are lots of good reasons to frost a cake with something other than buttercream. Whether you're out of sugar and butter or just looking for a healthier alternative, there are plenty of other icing options that will taste great and create a beautiful dessert.
One of the simplest ways of "frosting" a cake without any icing is to dust it with powdered sugar, cocoa powder or cinnamon. Powdered sugar looks good on chocolate cakes and those with fresh fruit, where it pops against the strong colors, and cocoa powder is visually striking on white or yellow cakes.
Put a tablespoon or two of your chosen powder in a fine mesh sieve. Shake the sieve gently and evenly over the top of your cake, applying as much or as little powder as you'd like on top.
Since powdered toppings can become moist and gooey over time, apply this "frosting" as near as possible to when you plan to serve the cake.
Chocolate ganache is a rich, decadent topping that you can use in just the same way as buttercream if you whip it to a fluffy texture. Ganache is made from just two ingredients -- chocolate and heavy cream -- and you can also pour it directly onto the top of cakes when it's warm and melted. No cream? Melt a small amount of chocolate and drizzle that on top of your cake for an elegant, simple look.
If you melt your chocolate in the microwave, use 50 percent power to avoid overheating the chocolate and making it grainy, thick and tough to spread.
Although cream cheese isn't very sweet by itself, it makes a worthwhile "icing" substitute for a cake that is quite sweet. It also has the benefit of resembling buttercream frosting, so it's a good alternative if you want to prepare a traditional-looking cake.
To make cream cheese spreadable, let it sit out of the fridge until it reaches room temperature, then use a knife or spatula to spread it onto your cake. For a fluffier texture, whip the cream cheese before spreading it.
Fresh fruit also works well as a cake topping and adds a beautiful pop of color, especially in combination with cream cheese or ganache. Try sliced strawberries, kiwis or blueberries. Add fruit just before you plan to serve the cake so that it doesn't release too much moisture.