Preheat oven to 350°F. Grease an 8x8 baking pan and line with parchment paper, leaving enough overhang on the sides to lift the bars out easily once cooled.

Combine almond flour, sweetener and melted butter in a bowl and mix until combined. Transfer to the prepared pan and press down evenly with your fingers or the back of a spoon. Bake for 12-15 minutes until golden. Remove from oven and set aside to cool completely.

In a large bowl beat the softened cream cheese, egg, vanilla extract and powdered sweetener with a hand mixer or stand mixer until smooth. Scrape down the sides and mix again until no lumps remain. Divide the mixture evenly in half. Spread one half over the cooled crust.

Blend the frozen blueberries with the lemon juice and zest until smooth. Transfer to a saucepan over low/medium heat and reduce for 10 minutes, stirring occasionally. Sprinkle in the xanthan gum, stir to combine and continue to cook until thickened. Remove from heat and cool completely.

Whisk the cooled blueberry puree into the remaining cream cheese mixture until fully combined and smooth. Spread evenly over the plain cheesecake layer.

Bake at 350°F for 30 minutes. The center will have a slight jiggle when done, this is correct, it sets in the fridge.

Remove from oven and allow to cool completely at room temperature. Once cooled refrigerate for at least 1 hour to firm up. Use the parchment overhang to lift the slab out of the pan. Cut into squares and serve.