
Adjust oven rack to middle position and heat the oven to 400 degrees F. Line a large baking sheet with parchment paper or use a silicon baking mat.
Whisk together flour, sugar, baking powder, baking soda, and the salt in a medium bowl.
Use a pastry blender to work the butter into the flour mixture until it resembles a coarse meal with a few small crumbles of butter the size of peas. (Or use a food processor).
In a small bowl, whisk sour cream, egg, and lemon zest until blended then add to the flour and butter mixture. Use a rubber spatula to mix until a crumbly dough forms. Gently stir in the blackberries. Don’t worry if some of the berries are crushed a bit.
Transfer the dough and all dry, floury bits to a lightly floured work surface. Knead the dough 3 to 5 times until it just comes together. Form into an 8-inch circle. Cut into 8 triangles, or use a biscuit cutter.
Place scones onto the baking sheet and lightly sprinkle tops with sugar. Bake until light golden brown, 14 to 16 minutes. Cool at least 10 minutes before serving.