How to Make It
Preheat oven to 425°.
Combine the first 4 ingredients in a small bowl, stirring with a whisk.
Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, and salt in a medium bowl, stirring with a whisk. Cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal. Add buttermilk mixture to flour mixture, stirring just until moist. Turn dough out onto a lightly floured surface; pat into a 7 1/2-inch square; cut into 12 rectangles. Place dough on a foil-lined baking sheet coated with cooking spray. Bake at 425° for 13 minutes or until lightly browned on edges and bottom.