Ah yes, time for a rhubarb recipe! And this is one of the few times I have no clue where I found the recipe. (If anyone knows, please mention in comments.)
Do I need to tell you how wonderful this was? We gobbled it down in no time. Although I think I got a tad carried away with the whipped cream in this photo!
1 lb fresh rhubarb stalks, cut into 1/2-inch pieces (3 cups), or 3 cups frozen rhubarb, thawed after measuring
1 cup packed light brown sugar
2 cups cake flour (not self-rising), sifted
3/4 teaspoon baking powder
1/2 cup plus 2 tablespoons granulated sugar
1 stick (1/2 cup) cold unsalted butter, cut into 1/2-inch cubes
1/3 cup whole milk
2 large eggs (1 separated)
sweetened (and flavored, your choice) whipped cream for serving
Put oven rack in middle position and preheat oven to 400°F. Butter a 10-inch glass or ceramic pie plate or a 2 1/2-quart oval gratin dish and chill.
Toss rhubarb with brown sugar in a bowl until coated.
Whisk together flour, baking powder, and 1/2 cup granulated sugar in a large bowl until combined well. Blend in butter with a pastry blender or your fingertips until mixture resembles coarse meal. Whisk together milk, whole egg, and yolk. Make a well in center of flour mixture and add milk mixture, stirring with a wooden spoon to gradually incorporate flour and form a soft, sticky dough.
Transfer half of dough to chilled pie plate and pat out over bottom and halfway up side with well-floured hands, then spoon rhubarb and any juices onto dough. Using a tablespoon, spoon remaining dough in small mounds evenly over top. Lightly beat egg white with a few drops of water, then lightly brush cake with egg wash. Sprinkle remaining 2 tablespoons granulated sugar over top.
Bake cake until top crust is golden and rhubarb is tender, 30 to 40 minutes. Transfer to a rack to cool, about 30 minutes.
Serve cake warm or at room temperature.