Preheat oven to 400. Mix together dry ingredients. Blend butter with pastry blender. Fold in blueberries. Pour in egg, buttermilk, lemon juice and lemon zest. Fold together.
Press dough on floured surface into a 3/4" circle. Cut into 10 triangles. Put on cookie sheet covered with parchment. Brush with buttermilk. Sprinkle with sugar and/or cinnamon, and lemon zest.
Bake 20 minutes until golden brown.
Cook on racks.
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