Brainy Buns: Summer Rhubarb Cake

The Art.
My grandmother has always been protective of her rhubarb plants, to put it mildly. I have never been able to figure this out, since you can't kill the stuff. You can try and corral it into one part of your garden and not only will it take over completely, it will grow under cement foundations and show up in your neighbor's yard on the other side. Nevertheless, my aunt would have to sneak into Grandma's garden at the break of dawn on summer mornings if she wanted to snag a few stalks for her famous rhubarb cake. When the family would visit for dinner that evening, my aunt would serve squares of warm rhubarb cake with a scoop of vanilla ice cream dribbling over the edges. Grandma would eye her plate suspiciously until we all felt sufficiently uncomfortable, then inquire where my aunt got the rhubarb. The grocery store, Grandma, the grocery store. We'd all smirk down at our plates while we tucked into our favorite summer dessert.
To be honest, the real beauty of my aunt's rhubarb cake is that you virtually can't mess it up. I've dressed the recipe up a bit over time, but you can throw everything in a bowl and stir it with a fork and it will turn out fine. In fact, my aunt would add a tablespoon of vinegar to a cup of milk and use that instead of buttermilk in a pinch. This is a homey, simple cake that goes hand-in-hand with the heartiness of the rhubarb plant.

Structure of Oxalic Acid

The Science.
However, there is a darkness that lingers within this plant. Rhubarb (Rheum rhabarbarum L.) is sour and sinister. Its tissues harbor oxalic acid, a dicarboxylic acid that is a weak poison. While this compound is found in many foods like sugar beets and spinach, the leaves of the rhubarb plant contain up to 20 times more oxalic acid than spinach leaves, and should not be eaten. Conversely, the rhubarb stalks have very little oxalic acid and are considered benign. The roots of the rhubarb plant have also been used in Chinese medicine since the 16th century [1]. But today, we will enjoy its tart flesh in a tasty cake to celebrate heartiness and surviving against the odds!

The Recipe.

Cake:
2 cups flour
1 teaspoon baking soda
1 teaspoon salt
1 cup brown sugar
½ cup butter
1 large egg
1 cup low fat buttermilk
1 teaspoon vanilla
2 cup chopped rhubarb

Topping:
1 cup brown sugar
1 cup chopped pecans
3 tablespoons melted butter

Combine flour, baking soda, and salt in a medium bowl. In a large bowl, cream together butter and sugar on medium speed. Add egg and vanilla, beat until combined. Alternately add flour mixture and buttermilk while beating on medium speed until just combined.