01 - Preheat oven to 325°F. Line the bottom of a 9-inch springform pan with parchment paper and lightly grease the sides.
02 - In a mixing bowl, combine the almond flour, erythritol, melted butter, cinnamon, and salt. Stir until a crumbly, uniform dough forms. Press the mixture firmly and evenly into the bottom of the prepared pan. Bake for 10 minutes, then remove and set aside to cool completely.
03 - While the crust bakes, combine the chopped rhubarb, erythritol, lemon juice, and water in a small saucepan. Cook over medium heat, stirring frequently, until the rhubarb breaks down and the mixture reaches a thick, jam-like consistency, about 8 minutes. Remove from heat and let cool.
04 - In a large bowl, beat the softened cream cheese and erythritol with an electric mixer until completely smooth and free of lumps. Add the sour cream and blend until incorporated. Add the eggs one at a time, mixing on low speed after each addition until just combined. Stir in the vanilla extract and lemon zest. Avoid overmixing to prevent excess air incorporation.
05 - Pour the cheesecake filling over the cooled crust, spreading it into an even layer with a spatula. Drop small spoonfuls of the rhubarb compote across the surface. Take a butter knife and gently drag it through the compote dollops in figure-eight motions to create decorative swirls throughout the batter.
06 - Tap the springform pan firmly on the counter two or three times to release trapped air bubbles. Place in the center of the oven and bake for 45 to 50 minutes, until the edges are set and the center retains a slight jiggle when gently shaken. Turn off the oven, crack the door open several inches, and let the cheesecake rest inside for 1 hour to cool gradually and prevent cracking.
07 - Transfer the cheesecake to the refrigerator and chill for at least 2 hours, or until fully set and firm. Slice with a sharp knife dipped in hot water for clean portions. Serve chilled.