Place black raspberries in freezer 1+ hours before makings scones.
Preheat oven to 425˚ and cover a sheet tray in parchment paper (or silpat).
In a large bowl, sift together all the dry ingredients. Cut in butter (using pastry blender, two knives, hands, or a food processor) until butter is in little pea size pieces. In a smaller bowl, whisk together egg white, maple syrup, and buttermilk. Combine with dry ingredients until dough pulls together.
Toss frozen black raspberries with lemon zest and flour. Fold in to scone dough.
Pat dough into a circle and cut into 6-8 triangles. Place on the sheet tray 1-2 inches apart. Whisk together egg yolk and water; brush over scones. Place tray in oven and bake for 15-18 minutes until scones are golden and firm to the touch.