Preheat the oven to 350°F and line an 8x8 inch baking pan with parchment paper, leaving an overhang. Mix the almond flour, powdered sweetener, salt and melted butter, press firmly into the pan and bake for 10 minutes. Reduce the oven to 325°F.
Beat the cream cheese and powdered sweetener until smooth. Add the sour cream, vanilla and egg and mix on low speed just until combined.
Spread the cheesecake layer over the crust and bake for 22 to 26 minutes, until the edges are set and the center has a slight jiggle. Let it cool at room temperature for 1 hour.
Melt the butter in a saucepan over medium heat, then whisk in the brown sugar substitute and heavy cream. Simmer for 4 to 5 minutes, stirring often, until the mixture thickens and turns a deep caramel color.
Remove the pan from the heat and stir in the vanilla, salt and chopped pecans until every piece is coated. Let the topping cool for 10 minutes so it thickens further.
Spoon the pecan pie topping over the cooled cheesecake and spread it gently to the edges.
Chill for at least 4 hours until the topping is set and gooey, then lift out using the parchment and slice into 16 bars.