2Mix 1 cup flour and confectioners' sugar together in a bowl; cut butter into flour mixture using a pastry cutter or two forks until mixture is crumbly. Press flour-butter mixture into an 8-inch square pan.
3Bake crust in the preheated oven until golden brown, 15 to 20 minutes.
4Mix white sugar, 1/4 cup flour, baking powder, and nutmeg into the beaten eggs. Fold rhubarb into egg mixture; pour rhubarb filling into the baked crust.
5Bake in the preheated oven until filling is bubbling, 35 minutes.
Footnotes
Cook's Note:
If using frozen rhubarb, add an extra tablespoon of flour to the filling.