Preheat oven to 350°. Have your pie shell ready to go.
Whisk the sugar and butter together until smooth.
Whisk in the eggs, one by one, until mixture is smooth.
Mix the buttermilk powder and flour in a small bowl, then add to the egg mixture and stir until smooth. Stir in nutmeg, vanilla bean paste and water until smooth.
Bake for 45 minutes or until almost set. Transfer to a wire rack, and cool 1 hour.
Chill thoroughly before serving (or not -- I like things chilled, but some prefer room temperature).