Preheat oven to 400 degrees F. In a mixing bowl, combine berries with sugar, cinnamon, cornstarch and lemon juice. Stir gently to combine. Spread berry mixture out on a 10-inch tart or gratin dish. Dollop spoonfuls of scone dough evenly over the top of the fruit; leave a border around the edge of the dish for spreading. Drizzle the surface with melted butter and dust with sugar. Set on a cookie sheet and bake for 25 to 35 minutes until the top is golden brown and the fruit juices bubbling.
Cool for 15 minutes before serving. Serve with heavy cream, whipped cream or vanilla ice cream.
In a large bowl, sift together flour, baking powder, salt and sugar; mix thoroughly. Cut in butter using 2 forks or a pastry blender. The butter pieces should be coated with flour and resemble crumbs.
In another bowl, mix buttermilk and egg together, and then add to the flour mixture. Mix just to incorporate, do no overwork the dough.
Roll blueberries in flour to coat, this will help prevent the fruit from sinking to the bottom of the scone when baked. Fold the blueberries into batter, being careful not to bruise.