01 - Preheat the oven to 325°F (163°C). Lightly grease a 9-inch springform pan and line the bottom with parchment paper.
02 - In a medium bowl, combine the almond flour, powdered erythritol, melted butter, cinnamon, and salt. Mix until the texture resembles damp sand. Press the mixture firmly and evenly into the bottom of the prepared pan. Bake for 10 to 12 minutes until just golden around the edges. Remove from the oven and set aside to cool.
03 - While the crust bakes, combine the chopped rhubarb, water, and powdered erythritol in a small saucepan. Bring to a gentle simmer over medium heat and cook for 8 to 10 minutes, stirring occasionally, until the rhubarb softens and the mixture thickens to a jam-like consistency. Remove from heat, stir in the vanilla extract, and let cool completely.
04 - In a large mixing bowl, beat the softened cream cheese and powdered erythritol with a hand or stand mixer on medium speed until completely smooth and free of lumps. Add the eggs one at a time, mixing thoroughly after each addition. Blend in the sour cream, vanilla extract, lemon zest, and heavy cream until the batter is fully incorporated and silky.
05 - Pour the cheesecake filling over the cooled crust, spreading it into an even layer. Drop spoonfuls of the cooled rhubarb compote across the surface of the batter. Using a knife or skewer, gently drag through the compote dollops to create a marbled swirl pattern throughout the cheesecake.
06 - Bake for 40 to 45 minutes, or until the edges are firmly set and the center still has a slight jiggle when gently shaken. Turn off the oven, crack the oven door open, and allow the cheesecake to cool gradually inside for 1 hour to prevent cracking.
07 - Remove the cheesecake from the oven and let it cool to room temperature. Transfer to the refrigerator and chill for at least 2 hours, or until fully set. Slice into 12 portions and serve chilled.