01 - Preheat oven to 325°F. Lightly grease a 9-inch springform pan and line the bottom with parchment paper.
02 - In a medium bowl, combine almond flour, powdered erythritol, melted butter, cinnamon, and salt until the mixture resembles damp sand. Press evenly into the bottom of the prepared pan. Bake for 10 to 12 minutes until just golden. Remove and let cool.
03 - In a small saucepan, combine rhubarb, water, and erythritol. Bring to a simmer and cook for 8 to 10 minutes, stirring occasionally, until the rhubarb is soft and the mixture thickens. Remove from heat, stir in vanilla extract, and let cool.
04 - In a large bowl, beat softened cream cheese and erythritol until smooth. Add eggs one at a time, mixing well after each addition. Blend in sour cream, vanilla extract, lemon zest, and heavy cream until fully incorporated and creamy.
05 - Pour the cheesecake filling over the cooled crust. Dollop spoonfuls of the rhubarb compote over the batter. Use a knife or skewer to gently swirl the compote into the filling for a marbled effect.
06 - Bake for 40 to 45 minutes, or until the edges are set and the center is slightly jiggly. Turn off the oven, crack the door open, and let the cheesecake cool inside for 1 hour.
07 - Remove from the oven and cool to room temperature. Refrigerate for at least 2 hours before slicing and serving.