Grate 1 tsp. zest from 1 orange, then juice it. Cut the peel and white pith from the remaining oranges; cut between the membranes to release the segments. In a large skillet, melt the butter over medium. Add the sugar and juice; simmer until thickened, 3 to 5 minutes. Add the liqueur and orange zest; simmer 1 minute. Add the orange segments; stir until warm, about 1 minute. Arrange the crepes on plates; top with the oranges and sauce. Dust with sugar.