Rub lemon juice along the rim and one side of a heatproof glass. Roll into sugar, letting it adhere to the glass. If desired, use a kitchen torch to caramelize the sugar to the glass.
Place glass under the coffee dispenser. Brew a 4-ounce coffee.
Add the coffee liquor, rum, and top with whipped cream. Sprinkle the nutmeg on top. Enjoy!