Fill a pot for the pasta with about 6quarts of water, cover, and place over high heat.
Put the butter in a 12-inch skillet and place over medium high heat. When the butter has melted add the orange zest and mint and season generously with salt and pepper. Add the orange juice and cook until it has reduced by a third and has thickened slightly. Remove from the heat.
Add 2tablespoons salt to the boiling pasta water, add the fettuccine, and stir until all the strands are submerged. Cook until al dente. When the pasta is done, drain well and transfer to the pan with the sauce in the pan. Add the grated Parmigiano-Reggiano and serve at once.