Place oven rack in the top third of the oven. Preheat oven to 450 degrees.
In a large bowl, whisk together flour, baking powder, baking soda, and salt.
Add shortening and cut in with pastry blender until the mixture is mealy.
Gradually add buttermilk, stirring with a wooden spoon just until the dough is soft and slightly sticky. Do not over mix!
Transfer the dough to a lightly floured surface. Using a light touch, turn the edges toward the middle, pressing with your hands. Press the dough out 1/2 inch thick and cut straight down with a 2-inch biscuit cutter. Pat the scraps together and cut out more rounds.
Arrange on a baking sheet no more than 1/2 inch apart and bake until lightly browned, 12 to 15 minutes.