Position a rack in the middle of the oven and preheat to 350 degrees. Lightly butter a 10 inch cake pan. Dust with sugar and cinnamon.
Sift the dry ingredients into a large bowl, pouring back into the bowl any bits of grain or other ingredients that may remain in the sifter.
Using a spatula, gently fold the wet ingredients into the dry ingredients. For tender cake, it is important that you use a light hand while folding the batter with the spatula. The batter should be slightly thick and smooth without any clumps of flour. Scatter rhubarb compote around the bottom of the pan. Scrape the batter over the rhubarb.
Bake for 60 - 70 minutes, rotating the pan halfway through. The cake should be dark golden-brown and spring back when lightly touched; a skewer inserted into the center should come out clean. Remove the cake from the oven and cool in the pan for 10 minutes. Then, invert the cake out of the pan and cool on a baking rack. The cake should be eaten at room temperature.
Rhubarb Compote
Rinse and slice rhubarb stalks. Cut the rhubarb into ¾ inch chunks. Place the chunks into a medium heavy-bottomed pot (with about a 5-quart capacity).
Add the brown sugar, stir and turn the heat to medium-low. (It’s important to begin slowly so the rhubarb warms up and begins to release its liquid.) Cook the rhubarb mixture for about 15 minutes, covered, until the mixture is saucy.