Preheat oven to 400 degrees F. Spray a large baking sheet with vegetable-oil cooking spray.
In a large bowl, combine flour, sugar, poppy seeds, cream of tartar, baking soda, and salt. With a pastry blender or two knives, cut butter into flour mixture until particles are the size of small peas.
In a medium bowl, beat (1) one egg lightly with orange juice and orange zest. Add to flour mixture; stir just until mixed.
On a lightly floured surface, knead dough gently. Pat or roll out the dough into a circle 1/2-inch thick. Using a lightly greased and floured 2- or 3-inch biscuit cutter, cut into rounds, cutting close together to generate as few scraps as possible. Dip cutter into flour as often as necessary to keep dough from sticking. Push scraps of dough together so that edges join; firmly pinch edges with fingertips to make a partial seal. Pat this remaining dough to 1/2-inch thick; continue to cut 3-inch rounds. Space 1-inch apart onto prepared baking sheet.
In a small bowl, combine 1 egg and 1tablespoon milk; brush onto top of scones. Bake 10 to 15 minutes or until golden brown. Remove from oven and serve either at room temperature or warm.
NOTE: I combined some powdered sugar (confectioners') sugar and orange juice together to make a think icing to top the scones after baking. If making Lemon Scones, use lemon juice.
Yields 8 to 10 large scones and 12 to 14 smaller scones.