Combine sugar and orange zest to make an orange sugar.
In another bowl, combine cranberries and most of the orange sugar mixture (reserving about a tablespoon).
Roll out the pie dough to approximately 10-12 inches in diameter. Mound the cranberry mixture onto the center of the dough, leaving about two inches of space around the edge. Dot the cranberry mixture with butter if desired. Fold the edges of the dough over the cranberries. Brush the folded over dough with beaten egg and sprinkle with the reserved orange sugar.
Bake for 45-50 minutes, or until the crust is golden brown. Let cool. Cut into wedges, and serve.