Preheat the oven to 350ºF. In a large bowl, whisk together almond flour, sweetener, and salt. Stir in the melted butter until well combined.
Press evenly into the bottom of a lightly greased 8-inch square pan and bake 10 to 12 minutes, until the edges are just turning golden. Remove and let cool in the pan.
Cheesecake Filling
Reduce the oven heat to 300ºF.
In a large bowl, beat the cream cheese on medium for 1 to 2 minutes, until super creamy. With a silicone spatula, scrape the bottom and sides of the bowl, and the beaters, to get all the lumps of cream cheese. Beat again to smooth them out, then beat in the powdered sweetener until well combined.
Add the eggnog, rum, vanilla, and nutmeg and beat until incorporated. Scrape the bowl and beaters again with a silicone spatula. Then add the eggs one at a time, beating until just combined.
Pour the mixture over the cooled crust and spread to the edges. Bake 45 to 60 minutes, or until the sides are set and the center jiggles just slightly when the pan is shaken. Remove and let cool completely, then cover and refrigerate 3 hours or up to overnight.
Topping
Whip the cream and the sweetener until it holds stiff peaks. Pipe or spoon onto the cheesecake bars. Dust lightly with ground nutmeg.
Notes
You can also bake these bars in a 9x9 inch pan. They will be wider and shallower, and they will bake a bit faster so keep a close eye on them.Storage Information: Cover the cheesecake tightly with plastic wrap or waxed paper. It will last in the refrigerator for up to one week. You can also freeze the cheesecake bars but I recommend leaving off the whipped topping until you are ready to serve. They will be good in the freezer for at least 2 months.Sweetener Options: You really need an erythritol sweetener for a firm shortbread crust. The filling will work with just about any sweetener. But please see the Expert Tips for a little more information.