|1 1/4||cups milk|
|1||tablespoon cider vinegar|
|2 1/4||cups unbleached all-purpose flour|
|1||teaspoon baking soda|
|8||tablespoons unsalted butter, at room temperature|
|1 1/4||cups packed dark brown sugar|
|3||cups rhubarb sliced 1/2 inch thick|
|1/3||cup packed light or dark brown sugar|
|1/2||cup old fashioned rolled oats|
|1 1/2||teaspoon ground cinnamon|
Position a rack in the center of the oven and preheat to 350 degrees F. Lightly butter and flour a 9 x 13 inch baking pan, tapping out the excess flour.
Combine milk and vinegar and let stand until the milk curdles, about 5 minutes. Mix the flour, baking soda, and salt to combine.
In a medium-sized bowl, cream the butter and brown sugar together with an electric mixer on high speed until light and fluffy, about 3 minutes. Add the egg and mix throroughly.
In three additions beginning with the flour mixture, stir in alternating portions of flour and curdled milk, mixing with a spoon just until smooth. You can use the mixer on low speed but do not over-mix. Fold in the rhubarb. Spread the mixture evenly in the pan. Make the topping by mixing the brown sugar, oats, and cinnamon in a small bowl until blended. Sprinkle evenly over the batter.
Bake until a toothpick inserted in the center of the cake comes out clean, 35 to 40 minutes. Cool in the pan on a wire rack. For the real rhubarb lover, serve with a dollop of rhubarb jam on the side.
Recipe by Ellen Ecker Ogden from her book From the Cook's Garden (HarperCollins, 2003). Ellen is a garden writer and cookbook author based in Vermont.