Brown Sugar Rhubarb Shortcake

One last rhubarb recipe for the season as we transition into summer. This shortcake recipe is definitely a keeper.
Brown Sugar Shortcake
Adapted from America's Test Kitchen
2 cups (10 ounces/283 grams) all-purpose flour
3 tablespoons packed light brown sugar
1 tablespoon baking powder
½ teaspoon table salt
8 tablespoons unsalted butter (1 stick), cut into 1/2-inch pieces and chilled
1 large egg
½ cup sour cream
Adjust oven rack to upper-middle position and heat oven to 375 degrees. Line rimmed baking sheet with parchment paper. Pulse flour, brown sugar, baking powder, and salt in food processor until no lumps of sugar remain. Scatter chilled butter pieces over top and pulse until mixture resembles coarse meal, about 7 pulses. Transfer to large bowl.
Whisk egg and sour cream together in small bowl. Stir into flour mixture with rubber spatula until large clumps form. Using hands, knead lightly until dough comes together and no dry flecks of flour remain.
Pat dough into round, and then divide into 6 pieces. Place on parchment lined baking sheet. Bake until golden brown, 25 to 30 minutes. Cool for 10 minutes before topping with fruit and whipped cream.