Preheat oven to 375°F. Whisk sugar and orange zest in a small bowl. Carefully transfer 1 sheet of dough (keeping dough in 1 piece) to a flat work surface. Using your fingers, pinch perforated seams together. Cover with half of sugar mixture. Place second sheet of dough over, pinch perforated seams together, and cover with remaining sugar mixture. Tightly roll dough away from you to create a long tube. Slice crosswise into 8 even rounds. Transfer rounds, cut side up, to muffin tin. Bake buns until golden brown, 20–25 minutes. Transfer immediately to a wire rack and let cool.