Preheat oven to 425. Whisk together flour, sugar, baking powder, salt. Cut in butter until largest are pea-sized and others like bread crumbs. In separate bowl, whisk together egg, heavy cream and zest. Add all at once to flour mixture. Mix with rubber spatula just until moistened. Gather dough into a ball and knead against sides of bowl 5-10 times until loose pieces adhere. Transfer to lightly floured surface. Pat into 8" round about 3/4" thick. Cut into 8 wedges and place on baking sheet 1/2" apart. Brush tops with cream and sprinkle with sugar. Bake 12-15 mins until golden brown.