Turning 50, meant she was born in the 60's. What was popular in the 60's? How about tie dye? There's lots of examples of tie dye cakes on line. After reading about a few of them, I said I can do this??!!!
I decided to make a three layer cake, two 8" and one 9" layer. In hindsight, I wish I had done three 8" layers. It was really hard to get the frosting smooth on the ledge between the 8 and the 9" layer. In addition I made one 8" layer as a test. I wanted to cut into one and see how it looked.
The process is fairly easy but be sure to allow plenty of time. Start by preparing a white cake mix according to the directions. (I used two cake mixes). Divide them into 6 bowls, and make each bowl a different rainbow color. Line the bottom of two 9 inch cake pans with wax paper, and grease the side. Layer your cake batter in circles. The first directions I looked at suggested using a spoon, which is what I did on my test cake. It worked okay but for the additional layers, I decided to use a measuring cup with a spout. A little more work but a lot easier to pour into circles. Use about 3/4 of the bowl for your bottom color, then use a little less of each color as you continue. Layer your second cake pan in the opposite order.
Bake according to the directions on the box. Allow the cake to cool and frost with your favorite buttercream frosting. My frosting didn't look as smooth as I would have liked and the more I tried to smooth it the worse it looked. Then I remembered a technique I learned when I took cake decorating classes. Once your frosting has developed a bit of a crust, use a piece of parchment and use your fingertips to smooth the frosting along the parchment. Works great!!!