Preheat your oven to 425°F and line a baking sheet with parchment paper. In a large bowl, whisk together the all-purpose flour, oat flour, baking powder, baking soda, and salt until evenly combined. This ensures the leavening agents are distributed throughout, which helps the scones rise evenly and develop a light, tender crumb.

Add the cold cubed butter to the dry ingredient mixture and cut it in using a pastry cutter, fork, or your fingertips until the mixture resembles coarse breadcrumbs with some pea-sized pieces of butter remaining. Cold butter creates steam pockets as the scones bake, resulting in a flaky, tender texture—this is why keeping the butter cold is essential.

In a separate small bowl, whisk together 1 egg, buttermilk, maple syrup, vanilla extract, and lemon zest until well combined. Pour this wet mixture into the crumbly butter and flour mixture, then gently fold everything together with a spatula or wooden spoon until just combined. I like to stop stirring as soon as I no longer see dry flour streaks—overmixing develops gluten and makes the scones tough and dense instead of tender.

Toss the black raspberries with 1 tablespoon of flour in a small bowl—this coating prevents them from sinking to the bottom of the scones and breaking apart during mixing. Gently fold the coated raspberries into the dough using as few strokes as possible to keep them intact and distribute them evenly throughout.

Turn the dough out onto a lightly floured work surface and gently press it into a flat disk about 1/2 inch thick (thicker scones stay moister inside). Using a sharp knife, cut the disk into 8 wedges like you're cutting a pizza. Try to use clean, decisive cuts without sawing motions, as this helps the scones rise more evenly and creates better-defined edges.

Place the scone wedges on the prepared baking sheet about 1-2 inches apart. In a small bowl, whisk together the remaining egg and milk to create an egg wash. Brush the tops of each scone with this mixture, then sprinkle each one generously with coarse sugar for a sweet, crunchy texture. Bake for 15-18 minutes until the tops are golden brown and a toothpick inserted into the center comes out with just a few moist crumbs.

Remove the scones from the oven and let them cool on the baking sheet for 5 minutes before transferring to a wire rack. I find that a few minutes of resting on the baking sheet helps them set up enough to handle without falling apart, while cooling them completely on a rack prevents them from steaming and becoming soggy on the bottom.