In a large mixing bowl combine flour, the 1/3 cup sugar, baking powder, lemon peel, salt and baking soda. Using a pastry blender, cut in butter or margarine until mixture resembles coarse crumbs. In a small bowl combine half-and-half, lemon juice, whole egg and egg yolk (mixture may appear curdled); add to dry mixture. Using a fork, stir just until moistened.
Turn dough out onto a lightly floured surface. Quickly knead 10 to 12 strokes or until dough is nearly smooth. Pat out to 1/2-inch thickness. Cut with a 2-inch round biscuit cutter. Place 2 inches apart on an ungreased baking sheet. Brush tops with mixture of egg white and water; sprinkle tops with coarse sugar. Bake in a 400 degree oven for 12 to 15 minutes or until golden. Remove from baking sheet; cool slightly. If desired, split scones and spread bottom halves with lemon curd; replace tops. Makes 10 to 12 servings.
Bake