The rainbow cake comes from a 21-year-old student named Kaitlin Flanner who wants to give a special gift to a friend who will be birthday. Because friends love the rainbow, Kaitlin also creates a plain cream cake that if cut will appear beautiful colors such as rainbows.
Kaitlin's friends who loved the unique pastries were immediately photographed and shared them on blogs and social networks. As a result the cake is often referred to as a rainbow sponge is a new trend in the culinary world.
In April 2010, the American TV show The Martha Stewart Show featured Rainbow cake and its creator. Kaitlin was invited to demonstrate how to make this rainbow cake in front of the glass screen according to his own recipe. Kaitlin's presence on the screen made himself, and of course the cake became more famous.
Because it has become a new trend in 2012, almost in every pastry shop, especially in big cities, already provide cakes. From three layers to seven layers. The specialty, the cream used to coat can be various colors. For those who do not like cream cheese, can use fruit-flavored cream.
Unfortunately, to bring the beauty of this Rainbow cake, the use of artificial coloring has become a necessity. But if one bite, it does not seem to have much impact on health.

If you want to make it later or tomorrow I will give you the step, how to make this rainbow cake

Preheat oven to 350 degrees. Brush six 9-inch-round cake pans (or as many 9-inch cake pans as you have, reusing them as necessary) with shortening. Line bottom of each cake pan with parchment paper; brush again and set aside.
In a large bowl, whisk together flour, baking powder and salt; set aside. In the bowl of an electric mixer fitted with the paddle attachment, cream together butter and sugar. Slowly add egg whites and mix until well combined. Add vanilla and mix until fully incorporated. Add flour mixture and milk in two alternating additions, beginning with the flour and ending with the milk. Mix until well combined.
Divide batter evenly between six medium bowls. Add enough of each color of food coloring to each bowl, whisking, until desired shade is reached. Transfer each color to an individual cake pan. Transfer to oven and bake until a cake tester inserted into the center of each cake comes out clean, about 15 minutes (working in batches if necessary).
Remove cakes from oven and transfer to a wire rack; let cool for 10 minutes. Invert cakes onto a wire rack; re-invert and let cool completely.
Using a serrated knife, trim tops of cakes to make level. Place four strips of parchment paper around perimeter of a serving plate or lazy Susan. Place the purple layer on the cake plate. Spread a scant 1 cup buttercream filling over the first layer with a small offset spatula so it extends just beyond edges. Repeat process with blue, green, yellow, and orange layers.
Place the remaining red layer on top, bottom-side up. Gently sweep away any loose crumbs with a pastry brush. Using an offset spatula, cover the top and sides with a thin layer of frosting (also use any of the excess frosting visible between the layers). Refrigerate until set, about 30 minutes.