Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C).

Mix sugar and flour together in a mixing bowl. Beat in eggnog, eggs, and vanilla until mixture is smooth. Stir in butter.

Pour mixture into prepared deep dish pie crust; dust with cinnamon and nutmeg, if using.

Bake in the preheated oven until custard is set, 45 to 60 minutes. The outer edges of the pie should be fully set and the center should still be a little jiggly.

Remove from oven and let cool to room temperature before slicing and serving.

Serve and enjoy!