01 -
Preheat the oven to 400˚F.
02 -
Mix rhubarb with sugar and just enough water to prevent scorching. Bring to a boil over medium-high heat, reduce heat, and cook 4-5 minutes until the rhubarb is partially cooked.
03 -
Mix cornstarch with 1/4 cup of water. Add a small amount of hot juice from the rhubarb to the cornstarch mixture, stir, then pour it back into the rhubarb mix. Cook and stir until bubbling, then cook an additional 1-2 minutes before removing from heat.
04 -
Mix the flour, 1/3 cup of sugar, and baking powder together in a bowl.
05 -
Cut in the cold butter until the mixture resembles crumbs. In a separate bowl, mix the egg and buttermilk together, then lightly combine with the flour and butter mixture. Stir only until the dough comes together.
06 -
Pour the warm rhubarb mixture into a 1 1/2 quart baking dish. Drop the biscuit dough on top in six portions. Sprinkle with the remaining 1 tablespoon of sugar. Bake for 20-25 minutes until the biscuits are cooked through and the fruit is bubbling.