Soufflés have a reputation for being hard to make, but they're actually quite simple: just create the base, fold in the egg whites, and watch it rise. If you have guests over, slide it into the oven during the salad course; when your meal is over, wow your guests when you bring this glorious finale to the table.
Set an oven rack in the middle of the oven and preheat oven to 375 degrees F. Butter a 4-cup souffle dish (the souffle won't rise as tall if using a larger dish) with 1 tbsp of the butter and dust it with granulated sugar, tapping out any excess. Prepare a collar for the souffle dish by buttering one side of a long 4-inch-wide strip of parchment paper with 1 tbsp butter, then dust it with some granulated sugar. Wrap the prepared side of the parchment paper around the outside of the souffle dish and tie it in place with kitchen string. It should rise above the rim of the dish by about 3 inches. Set the dish aside.
In a medium, heavy-bottomed saucepan, mix the orange rind with 7 tbsp of the granulated sugar, off the heat. Stir in the flour. Add the milk, stirring until smooth. Bring to a boil over medium heat, stirring constantly, and cook until thick, about a minute.
Continue to cook over medium heat until the mixture has thickened. Remove from the heat.
In a standing mixer fitted with a balloon whisk attachment, whip the egg whites and pinch of salt on low speed, to form small bubbles. Gradually increase to medium speed, and add the remaining 1 tablespoon of sugar. Increase to high speed and whip until stiff, but not dry, peaks form.To the flour mixture, whisk in the egg yolks, one at a time, whisking well after each addition.
Add the egg yolk mixture to a large mixing bowl, and whisk in the Grand Marnier, vanilla extract, and remaining 2 tbsp butter until smooth.Gently fold together the egg whites and yolk base, adding a third at a time, until all is incorporated.Pour the batter into the prepared dish, and bake in the oven for 30 minutes.
Remove the souffle from the oven, discard the paper collar, dust with powdered sugar, and serve immediately.