Place 1 1/4 cups all-purpose flour, 1 1/2 teaspoons granulated sugar, 1/2 teaspoon baking powder, and 1/2 teaspoon fine salt in a medium bowl and whisk to combine. Place 1/4 cup ice water and 1 1/2 teaspoons apple cider vinegar in a measuring cup or a small bowl and stir to combine.
Cut 1 stick cold unsalted butter into 1-inch cubes. Add to the flour mixture and toss to gently coat them. Use a pastry cutter or 2 knives to cut the butter into the flour. You should have various-sized pieces of butter, ranging from sandy patches to pea-sized chunks, with some larger bits as well.
Drizzle in about half of the ice water mixture and stir lightly with a fork until the flour is evenly moistened and the dough starts to come together. If the dough seems dry, add a little more ice water 1 to 2 tablespoons at a time. The dough will still look a bit shaggy at this point. If you grab a small piece of dough and press it slightly with your hand, it should mostly hold together.
Dump the dough out onto an unfloured work surface and gather it together into a tight mound. Using the heel of your hand, smear the dough a little at a time, pushing it away from you and working your way down the mass of dough to create flat layers of flour and butter.
Gather the dough back together with a bench scraper, layering the clumps of dough on top of one another. Repeat the process once or twice more; the dough should still have some big pieces of butter visible. Shape the dough into a disk and flatten it. Wrap in plastic wrap and refrigerate at least 2 hours or up to overnight.
