When rhubarb season rolls around in late May, I can count on my husband to reminisce about a rhubarb plant that grew outside his boyhood home. His mother used to warn him not to eat the potentially poisonous leaves, and then she’d chop the stalks to use in a pie. It worried him, but not enough to stop him from enjoying dessert. Strawberry-rhubarb pie is still one of his favorite treats, and still seems slightly dangerous because of the memory.
Is rhubarb really poisonous? Rhubarb leaves do contain high levels of oxalic acid (also present in smaller quantities in spinach and Swiss chard). It alarmed me to learn that this substance is used in industry as a bleaching agent and for rust removal. But when I read that I would have to eat over 10 pounds of extremely unpalatable leaves to ingest a lethal dose, I relaxed. The fleshy stalks contain much less of this toxin, most of which is neutralized during cooking anyway.
In fact, for thousands of years rhubarb was known not for its toxicity but for its health-giving properties. In Ancient China and later in Europe (Marco Polo is said to have had something to do with the spread of rhubarb across continents) it was employed for medicinal, not culinary, purposes. Rhubarb stems, which have an extremely tart flavor, were not used in cooking until sugar became affordable to common folks in the 17th century. From then until now, rhubarb has been prized for the delicious acidity it lends to simple pies, cakes, cobblers and muffins.
When shopping for rhubarb, look for shiny, crisp, unblemished stalks. Color will range from green to pink to bright red and is no indication of flavor or ripeness, but of the particular variety being sold. Remove and dispose of any scary leaves (you don’t want Fido to eat them out of the garbage can). Store the stalks in a plastic bag in the crisper drawer of your refrigerator. Rhubarb should keep for several days before becoming limp and rubbery. To prepare it for baking, strip away the stringy outer layer from larger stalks. If your stalks are small, you can skip this step.
When I feel like living on the edge at this time of year, I bake a taste-tingling rhubarb cake. I know rhubarb won’t kill me (actually, rhubarb is full of vitamins, minerals, and antioxidants), but I still get a thrill from the daring flavor this notorious ingredient lends to my homey dessert.
Rhubarb Streusel Coffee Cake
Serves 8 to 10
Rhubarb loses much of its bright color (but none of its flavor) during baking. If that bothers you, add 1/3 cup of stemmed and chopped strawberries to the rhubarb for a more vivid fruit filling.
For the streusel:
3/4 cup unbleached all-purpose flour
2/3 cup packed light brown sugar
1/2 teaspoon ground cinnamon
¼ teaspoon ground ginger
1/4 teaspoon salt
5 tablespoons unsalted butter, cut into bits, chilled
For the cake:
1/2 pound fresh rhubarb stalks, tough strings removed, cut into 1/4-inch dice
¾ cup plus 3 tablespoons sugar
2 large eggs
1/2 cup buttermilk
1 teaspoon pure vanilla extract
1 1/3 cups all-purpose flour
1/4 teaspoon baking soda
1/2 teaspoon salt
1/2 cup (1 stick) unsalted butter, softened
• Preheat the oven to 375 degrees. Grease the inside of 10-inch-round springform pan.
• Make the streusel: Combine the flour, brown sugar, cinnamon, ginger, and salt in a mixing bowl. Add the butter and work the mixture between your fingers to form large crumbs. Refrigerate until ready to use.
• Make the cake: Toss the rhubarb with 3 tablespoons sugar and set aside. Whisk together the eggs, buttermilk and vanilla in a large measuring cup.
• Combine the flour, baking soda and salt in a medium mixing bowl.
• Combine the butter and remaining ¾ cup sugar in a large mixing bowl and cream with an electric mixer on medium-high speed until fluffy, about 3 minutes, scraping down the sides of the bowl once or twice as necessary. With the mixer on low, slowly add the egg mixture and mix until well-combined, scraping down the sides of the bowl once or twice as necessary. Add the flour mixture, 1/2 cup at a time, scraping down the sides of the bowl after each addition.
• Scrape the batter into the prepared pan and smooth the top with a rubber spatula. Scatter the rhubarb over the batter. Scatter the streusel over the rhubarb. Bake the cake until it is golden and a toothpick inserted in the center comes out clean, 45 to 50 minutes. Let the cake cool in the pan for about 10 minutes. Release the sides of the pan and use a large spatula to slide the cake from the pan bottom to a wire rack. Cool completely, cut into wedges, and serve.