In a food processor fitted with the s-blade, combine the flour, salt, baking powder, sugar and vanilla bean powder. Pulse a few times.
Add the butter cubes (scattered through the flour mixture), and pulse 10-15 times to break up the butter.
Add the buttermilk to the mixture, and pulse another 10-15 times until it all comes together.
Dump the dough onto a lightly floured work surface, and gently work in the blueberries. Transfer to a parchment lined baking sheet and shape into a square, about 1" thick. Brush with nut milk, and transfer to fridge for 30 minutes.
Remove from the fridge, and using a bench scraper, cut into 12 evenly sized pieces. Gently separate the pieces on the baking sheet (they'll expand while they bake).
Bake in a 400 degree oven for 20-25 minutes, until deeply golden. Cool on a wire rack.
Sprinkle with powdered sugar before serving.