1 1/2 c. plus 3 Tbsp. flour
3 Tbsp. plus 1 c. sugar
1 1/2 tsp. baking powder
1/2 tsp. kosher salt
6 Tbsp. chilled butter, cut into pieces
1/2 c. plus 1 Tbsp. sour cream
6 c. fresh blueberries
2 Tbsp. fresh lemon juice
1 Tbsp. finely grated lemon zest
Preheat oven to 375°F. Whisk 1 1/2 c. flour, 3 Tbsp. sugar, baking powder, and salt in a large bowl. Add butter. Use fingertips to mix until pea-size lumps are formed. Gently mix in sour cream just until biscuit dough forms. Do not overmix..
Combine 1 c. sugar, 3 Tbsp. flour, berries, juice, and zest in a large bowl. Toss to coat. Pour into an 8x8x2″ glass baking dish. Tear biscuit topping into quarter-size crumbles; scatter over berries.
Bake until thick and bubbling and topping is cooked through and deep golden brown, 45–50 minutes. Let cool for at least 1 hour.