Preheat the oven to 400°. With a mixer, cream the butter and sugar together. Add the eggs and mix well. Add the eggnog, flour, vanilla, salt, and nutmeg. Mix well.
Pour into the unbaked pie crust. Place in the oven and immediately turn the heat down to 350°. Bake for 45 to 55 minutes, or until the pie is just set (but still has a little jiggle to it) and golden brown. Cool completely and sprinkle with powdered sugar, if desired. Cool completely before storing in the refrigerator.
If you see some butter on top of the pie after baking, don't worry. It will absorb back into the pie as it cools.
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