Preheat the oven to 325°F (163°C). Wrap the outside bottom and sides of a 9-inch springform pan with aluminum foil to prevent water from seeping in.
In a bowl, combine the almond flour, melted butter, erythritol, and salt. Press the mixture firmly into the bottom of the springform pan. Bake for 10 minutes until lightly golden, then set aside to cool.
In a large bowl, beat the softened cream cheese with erythritol on medium speed until smooth and creamy, about 3 minutes. Scrape down the sides of the bowl frequently to remove lumps.
Add the eggs one at a time, beating on low speed after each addition just until incorporated. Do not overmix.
Add the sour cream, vanilla extract, lemon juice, and salt. Mix on low speed until just combined and the batter is silky smooth.
Pour the filling over the cooled crust. Place the springform pan inside a large roasting pan and carefully pour hot water into the roasting pan until it reaches halfway up the sides of the springform pan.
Bake in the water bath for 60-70 minutes until the edges are set and the center still has a slight jiggle. Turn off the oven, crack the door open slightly, and let the cheesecake cool inside the oven for 1 hour.
Remove from the oven and the water bath. Refrigerate uncovered for at least 6 hours or overnight before unmolding and slicing.
