All of my favorite things in one. Fresh ginger goes great with the rhubarb and the oatmeal cake, well, is gooey and tasty. Let it cool at least 20 minutes before slicing. I top it with frothed cream but vanilla ice cream would be great too. As for the name, I have to credit Vivian my 4-year-old. She corrected me when I said upside-down cake and said it should be a "downside-up" cake. - thirschfeld —thirschfeld
Test Kitchen Notes
This is a great cake. I was a little skeptical about the whole downside-up/upside-down "thing" since this is done in a cast-iron skillet, but the cake came out beautifully! The syrupy ginger-rhubarb topping is wonderful and the cake itself is moist and delicious. I brought this to a gathering and everyone raved -- the only problem was that I forgot to bring vanilla ice cream... I won't make that mistake again. - WinnieAb —The Editors
In a mixing bowl combine the oats with the boiling water. Add the1/4 cup of butter. Set aside to cool.
Preheat the oven to 350 degrees. Gently melt the butter in a 10 inch cast iron skillet. Remove it from the heat. Spread the brown sugar evenly across the bottom. In a large bowl mix the ginger and rhubarb. Spread the rhubarb evenly across the brown sugar. Set aside.
In the empty rhubarb bowl combine the flour, baking powder, baking soda and salt.
To the cooled oatmeal add the egg, both sugars, and vanilla. Mix to combine. Add the dry ingredients to the wet and mix until combined.
Spread the cake batter evenly across the top of the rhubarb. Place into the oven and bake for 30-40 minutes.
Remove from the oven when done and let cool for 5 minutes before inverting onto a cake plate. Let cool for 20 minutes before slicing.