Buttermilk-Rhubarb Coffee Cake
Preparation time: 45 minutes, including baking
Yield: One 8-inch square cake

1 1/2 cups chopped rhubarb (in 1/4-inch pieces)
2 tablespoons sugar
Nonstick spray for the pan
1/2 cup (1 stick) unsalted butter, softened
2/3 cup sugar
2 large eggs
1 teaspoon vanilla extract
1 1/2 cups unbleached all-purpose flour
1/2 teaspoon salt
1 teaspoon baking powder
1/8 teaspoon (large pinch) baking soda
1/2 cup buttermilk
  1. Preheat the oven to 350°F (325°F for a glass pan). Place the chopped rhubarb in a bowl, and sprinkle with 2 tablespoons sugar. Let stand while preparing the batter.
  2. Spray an 8-inch baking pan with nonstick spray.
  3. Place the softened butter in a mixing bowl. Add the sugar, and cream together until fluffy. Add the eggs, one at a time, beating well after each. Stir in the vanilla.
  4. In a second bowl, stir together the dry ingredients until uniformly blended.
  5. Add the dry mixture to the butter mixture, alternating with the buttermilk. Stir thoroughly, but minimally - until combined. Don't overmix.
  6. Fold in the rhubarb, and transfer the batter to the pan. The batter will be somewhat stiff, and might seem to resist being spread into the pan. Be patient, and give the spreading process a few minutes of your time and attention. If it doesn't look completely uniform in the pan, that's OK.
  7. Use the same bowl (no need to clean it) to mix together the brown sugar and cinnamon, and sprinkle this on top of the batter.
  8. Bake for 25 minutes, or until a toothpick inserted all the way into the center comes out clean. Serve warm or at room temperature.