Ingredients

• For the Crumb Crust

  • 1/2 cup (1 stick) unsalted butter, melted
  • 1 cup all-purpose flour
  • 1/2 cup sugar
  • 1/2 teaspoon coarse salt

• For the Cake

  • 3 cups (1 1/2 sticks) unsalted butter, room temperature, plus more for pan
  • 1 pound rhubarb, trimmed and cut on a very sharp diagonal about 1/4 inch thick
  • 1 3/4 cups sugar
  • 1 1/2 cups all-purpose flour
  • 1 1/2 teaspoons baking powder
  • 1 1/2 teaspoons coarse salt
  • 2 large eggs
  • 1 teaspoon finely grated lemon zest
  • 1 tablespoon freshly squeezed lemon juice
  • 1 cup sour cream