Prep the pan and oven. Preheat the oven to 325°F (163°C). Line an 8x8-inch baking pan with parchment, leaving overhang on two sides for easy lifting. Lightly grease the exposed sides.

Make the crust. In a bowl, combine almond flour, granulated sweetener, salt, and cinnamon. Stir in melted butter and vanilla until the mixture resembles damp sand and holds when pressed.

Press and par-bake. Press the crust into an even layer in the pan. Bake for 10 minutes until just set and slightly fragrant. Set aside to cool for 5 minutes while you make the filling.

Beat the cheesecake base. In a mixing bowl, beat softened cream cheese with powdered sweetener on medium speed until smooth and airy, about 1–2 minutes. Scrape the bowl.

Add eggs and flavorings. Beat in eggs one at a time on low speed until just combined. Mix in vanilla, sour cream, and a pinch of salt. Do not overmix to avoid excess air bubbles.

Divide and flavor. Pour about 2/3 of the cheesecake mixture over the crust and smooth the top. To the remaining 1/3 in the bowl, add pumpkin puree, pumpkin pie spice, extra cinnamon, and 1–2 tablespoons powdered sweetener. Mix until uniform.

Create the layers. Gently spoon the pumpkin mixture over the plain cheesecake layer. You can leave it as a distinct top layer or swirl with a knife for a marbled look.

Bake low and slow. Bake at 325°F for 28–35 minutes, until edges are set and the center jiggles slightly like Jell-O. Avoid browning the top; tent loosely with foil if needed.

Cool gradually. Turn off the oven, crack the door, and let the bars rest inside for 10 minutes. Then transfer to a rack and cool to room temperature.

Chill to set. Refrigerate, uncovered, for at least 4 hours (overnight is best). Use the parchment to lift out and slice into 12–16 bars with a sharp knife wiped clean between cuts.

Serve. Top with a dollop of lightly sweetened whipped cream and a sprinkle of cinnamon, if you like. Keep extras chilled.