Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour, sugar, salt, and baking powder in a bowl; cut in shortening with a pastry blender until mixture resembles coarse meal.
Make a well in center of flour mixture. Combine butter and boiling water. Pour butter mixture into center of well. Gently draw flour mixture into butter mixture until moist clumps form. Press dough into a 4-inch circle. Cover, and chill 30 minutes.
Slightly overlap 2 sheets of plastic wrap. Unwrap dough; place on plastic. Cover dough with 2 additional sheets of overlapping plastic wrap. Roll dough into a 13-inch circle.