Preheat your oven to 375 °F and prepare two ½ sheet pans by lining them with parchment paper or a silicone baking mat.
In a large mixing bowl, combine the flour, baking powder, granulated sugar, and salt. Mix well.
Add the cold butter chunks to the dry ingredients and use your fingers to work the butter into the mixture until it resembles coarse flakes.
If using, sprinkle the raisins over the mixture and gently incorporate them.
In a separate bowl, whisk together the buttermilk and eggs until well combined.
Pour the buttermilk mixture into the dry ingredients all at once and stir until just combined. It's okay if some loose flour remains at the bottom; avoid overmixing.
Transfer the dough onto a floured surface and knead it gently by hand until all the loose flour is incorporated.
Pat the dough into a thickness of about ¾" to 1".
Using a biscuit cutter, cut out scones that are 2 ½" to 3" in diameter. Re-roll any scraps and continue cutting until all the dough is used.
Place the scones on the prepared baking sheet, ensuring there is about 1" of space between each one.
Brush the tops of the scones with buttermilk and sprinkle with Demerara or granulated sugar.
Bake the scones on the middle racks of the oven, flipping the trays after 10 minutes for even baking.
