Preheat oven to 400 degrees, with rack in center. Place a baking mat on a baking sheet, and set aside.
In a large bowl, sift together flour, 3 tablespoons sugar, baking powder, and salt. Using a pastry cutter or two knives, cut in butter until the largest pieces are the size of peas. Stir in blueberries and zest.
Using a fork, whisk together cream and egg in a liquid measuring cup. Make a well in the center of dry ingredients, and pour in cream mixture.
Stir lightly with fork just until dough comes together. Turn out onto a lightly floured surface, and knead a few times to mix well.
Pat dough into a circle 1 1/4 inches thick on baking sheet. Brush tops with cream, and sprinkle with sugar. Bake until golden brown, 20 to 22 minutes and cut in to 8 pieces once cooled.
8 servings