Preparation Whisk together flour, sugar, baking powder, salt, baking soda, and cream of tartar in a large bowl, then blend in butter with your fingertips or a pastry blender until mixture resembles coarse meal. Stir in buttermilk and egg with a fork just until a soft dough forms. Turn out dough onto a lightly floured surface. With lightly floured hands, divide dough into thirds and knead each piece 3 or 4 times. Pat each piece into a 6-inch round (1/2 inch thick), then cut each round into 4 wedges. Heat griddle over low heat until hot, then lightly oil. Working in 2 batches, dust each wedge of dough with flour, patting off excess, then cook over low heat, undisturbed, 3 minutes. Increase heat to medium-low and cook until puffed and undersides are golden-brown, 3 to 5 minutes more. Turn scones over and cook until undersides are golden-brown, 6 to 8 minutes (watch closely; move scones and adjust heat as needed so they cook through without burning). Turn scones on edges and cook until golden-brown, about 1 minute per edge. Cut one scone open to check for doneness. Transfer to a rack and cool to warm. (Lightly oil griddle between batches.)
Preparation Whisk together flour, sugar, baking powder, salt, baking soda, and cream of tartar in a large bowl, then blend in butter with your fingertips or a pastry blender until mixture resembles coarse meal. Stir in buttermilk and egg with a fork just until a soft dough forms. Turn out dough onto a lightly floured surface. With lightly floured hands, divide dough into thirds and knead each piece 3 or 4 times. Pat each piece into a 6-inch round (1/2 inch thick), then cut each round into 4 wedges. Heat griddle over low heat until hot, then lightly oil. Working in 2 batches, dust each wedge of dough with flour, patting off excess, then cook over low heat, undisturbed, 3 minutes. Increase heat to medium-low and cook until puffed and undersides are golden-brown, 3 to 5 minutes more. Turn scones over and cook until undersides are golden-brown, 6 to 8 minutes (watch closely; move scones and adjust heat as needed so they cook through without burning). Turn scones on edges and cook until golden-brown, about 1 minute per edge. Cut one scone open to check for doneness. Transfer to a rack and cool to warm. (Lightly oil griddle between batches.)