The use of frozen rhubarb (whether store bought or frozen from the garden) is the best DoAhead for this recipe. I have not baked, froze and then thawed the cake. If you do, be sure to utilize this thawing trick. Remove the frozen cake from the freezer and place it, uncovered on a cooling rack. Once the cake is entirely thawed it can be covered.
It’s tempting to think the cake might dry out. Not true. I’ve found that many quick breads thaw better when exposed to air. If I thaw in covered containers or baggies the item can get “mushy”. Not fun! In the meantime, cut your prep time by using frozen rhubarb!