In a large bowl, combine flour, sugar, the baking powder, salt, and cream of tartar. With a pastry blender of two knives, cut in butter until mixture resembles coarse crumbs. Separate egg, placing white in a cup and the yolk in a small bowl. with a fork, beat egg yolk; stir in cream. Add yolk mixture with a fork until mixture clings together and forms a soft dough. Turn dough out onto lightly floured surface and knead gently 5 to 6 times. Gently knead in strawberries, divide dough in half. with a lightly floured rolling pin, roll one half of dough into a 7 inch circle. cut into 8 pieces. repeat with remaining half of dough. Place scones, 1 inch apart on greased baking sheet. pierce tips with tines of fork. Brush with reserved egg white; sprinkle with sugar in the raw. Bake scones at 15 to 18 minutes-or until golden brown. Serve warm.