In medium bowl, mix flour, sugar, salt and baking powder. Cut in cold, cubed butter until mixture resembles coarse crumbs. In small bowl, mix together egg and yogurt. Add egg mixture to flour mixture, mix until moistened. Add chopped strawberries and lemon zest. Turn mixture onto a floured surface and knead gently 6 to 8 times. Pat into a 6 inch circle, cut into 4 wedges. Separate and place on parchment lined baking sheet. Sprinkle with sugar, optional.