Rhubarb Custard Cake to Take

I tested this recipe with four different cake mixes and liked Pillsbury Moist Supreme Yellow Premium Cake Mix the best. (Add water, oil, and eggs as directed.) This delicious and popular cake tastes even better—and cuts nicely—if refrigerated overnight. Expect a few cracks on top and a moist, custard-like bottom, as some of the rhubarb sinks while baking.