Position rack in the center of the oven and preheat to 375 degrees. Into a large bowl, sift the flour, sugars, baking powder, baking soda, and salt. Add oatmeal & mix together. Distribute the butter cubes over the flour mixture. Using your fingertips, quickly rub the butter cutes into the flour mixture, until the mixture resembles coarse meal. In a medium bowl, stir together the buttermilk, egg, vanilla, & zest. Add the liquid mixture to the flour mixture. With a large rubber spatula, using as few strokes as possible, stir gently until the dough is moistened and begins to cling together. Handling the dough as little as possible, stir until all the ingredients are completely combined. Using a 0.33333333333333-c. measuring cup, drop the dough onto an ungreased baking sheet, leaving at least 3 cm between the scones. Bake 16 to 18 minutes, until the scones are golden brown. Cool the scones on the baking sheet set on a wire rack for 5 minutes. Using a mental spatula, transfer the scones to the wire rack and cool completely. Serve warm or store completely cooled scones in an airtight container at room temperature.