Preheat the oven to 325 degrees. Grease a bundt pan well with gluten free cooking spray or butter.
Place cake mix, melted butter, canola, eggs, eggnog, rum and nutmeg in the bowl of a stand mixer fitted with a paddle attachment (or use a hand mixer). Beat on low speed until all ingredients are incorporated (about 1 minute), beat on medium high for 1 minute more.
Pour batter into prepared pan and bake for 45-55 minutes, or until a toothpick inserted in the middle of the cake comes out clean. Cool in the pan for 10 minutes, then turn out onto a cooling rack to finish cooling.
Make the glaze by whisking the eggnog and rum or vanilla into the powdered sugar until the mixture is smooth and shiny. Drizzle decoratively over the cake. Top with an additional sprinkling of nutmeg if desired. Or just dust the finished, cooled cake with powdered sugar, instead of making the glaze.
Make it dairy free with melted coconut oil & dairy-free eggnog.