Sorry no picture for this cake as I made a big goof. Though it was still good I forgot to remove it from the pan so it stuck real good. It wasn't picture worthy. Maybe next time.
1/2 cup margarine
2 cups brown sugar
8-12 stalks rhubarb
2 cups all purpose flour
1&1/2 cups white sugar
1/2 cup oil
3 teaspoons baking powder
4 egg whites (unbeaten)
1 teaspoon vanilla extract
Cut fresh rhubarb into approximately 1/2 inch long pieces
Pre-heat over to 350F. In a 9x13 cake pan, melt 1 stick of margarine. This can be done in the oven while pre-heating it.
Brush the sides of the pan with the melted margarine so that the cake will not stick.
Coat the bottom of the pan with a layer of brown sugar (2 cups)
Cover the layer of brown sugar with the cut rhubarb. Cover the entire bottom of the pan.
Mix cake batter:
combine the flour and sugar then add the oil and 1/2 cup of mile. Stir until the flour is damp - then beat for one minute. Stir in the baking powder, the remaining milk, the unbeaten egg whites, and the vanilla. Beat for two minutes. Pour over the rhubarb in the cake pan.
Bake at 350F for 35-40 minutes (making sure a cake tester comes out clean. The center section will be the last to cook.) Mine took more like 65-75 minutes.
Remove from oven, cool slightly, run a knife around the sides to make sure it will come out cleanly, and invert it onto a serving plate. I use a cookie sheet. (This is step I forgot to do ;P) (If you have never removed an upside-down cake before it can be a little unnerving. You are dealing with hot melted sugar. So place the serving plate (cookie sheet) upside-down on the cake - grasp the cake pan an plate together - hold this at arms length while you quickly invert it. If you skip this step your caramel topping will stick itself to the pan. I know :P It is very hard to get out of the pan we had to eat it up-side down after we dug it out. This step is very important. Ask me I know from experience.
I top with cool whip when serving. I refrigerate cake too.