Preheat the oven to 400°.  Line a large baking sheet with parchment paper.

To make the dough, combine the flour, baking powder, and baking soda in a large mixing bowl.  Add the sugar and salt and stir to combine.  Cut the butter into the flour mixture using a pastry blender or fork.  The mixture should be coarse with pea-sized lumps of butter visible.  Add the buttermilk, blueberries and lemon zest all at once, and gently stir with a rubber spatula until the dough just comes together, taking care not to break up the blueberries.  Add more buttermilk if the mixture seems dry.

Turn the dough onto a lightly floured work surface and pat together in a long rectangular log, about 18 x 5 inches and 1-1/2 inches thick.  Cut the dough into 10 to 12 triangles and transfer to the prepared baking sheet.  Brush the tops with heavy cream and sprinkle generously with turbinado sugar.

Bake the scones until the tops are lightly browned, about 25 to 30 minutes.  Remove from the oven and allow to cool for 5 minutes before glazing.

To make the glaze, add the confectioners’ sugar, zest and juice to a small bowl.  In a small saucepan, melt the butter over medium heat.  It will melt, separate into milk solids and clear butter, foam and then start browning.  It will take longer than you think it will, but do not venture far and stir often, because once it starts to brown, it will go quickly.  Once the butter is browned and smells nutty, remove from the heat and add to the glaze ingredients.  Whisk to thoroughly combine.  The glaze should be free-flowing, and easily pourable, but not too thin.  You can add more lemon juice, cream or water to loosen the glaze if necessary.  Drizzle over the warm scones.