Heat the oven to 325°F and line an 8-inch square baking pan with parchment paper. Stir the almond flour, powdered allulose, cinnamon, and salt together, then mix in the melted butter until the crumbs are evenly moistened.
Press the crust firmly into the pan in an even layer. Bake for 8 minutes, then let it cool while you prepare the filling.
Beat the cream cheese and powdered allulose until smooth. Mix in the eggs one at a time, then blend in the sour cream and vanilla just until creamy.
Stir the melted butter, brown monk fruit sweetener, and cinnamon together for the swirl. Spread the cheesecake filling over the warm crust, then spoon the cinnamon mixture over the top in small ribbons.
Gently swirl the cinnamon mixture through the top half of the cheesecake with a toothpick or thin skewer, keeping most of the crust undisturbed.
Bake for 32 to 36 minutes, until the edges are set and the center still has a slight jiggle. Cool completely at room temperature.
Refrigerate for at least 4 hours before lifting from the pan and cutting into bars.