Two cake mixes - one in squares and the other in circles. I suggest shaping the circles to fit the square before icing the layers together. And don't forget to 'level' the top (or bottom after you flip it out of the pan).
I only had pink icing, and one can to boot, so I blended it with a whole thing of cool whip, which was probably the best tasting icing I have ever made!
Then I put cherry pie filling on the left and blueberry pie filling on the right. Easy as that. It was a big hit at the potluck we went to.