Preheat the oven to 350 degrees. In a large bowl whisk together the flax eggs, vanilla extract, 2 tablespoons of lemon juice, melted vegan butter and ½ cup of the keto sweetener.
Stir in the almond flour, baking powder and baking soda. Make sure you sift the baking soda if it has lumps. Mix until there are no dry streaks of almond flour and everything is well combined. This batter will be quite thick but spreadable.
In a smaller bowl whisk the room temperature cream cheese with the remaining sweetener, tapioca flour, lemon zest and remaining 2 tablespoons of lemon juice until very smooth. A hand mixer, if you have one, is convenient for this step but a whisk will work just fine.
Prepare an 8 by 8 inch baking dish by lining it with parchment paper. The parchment paper should be 8 inches wide but at least 14 inches long so it creates overhang "handles" to lift the blondies out of the pan once they are baked. Spread half the blondie batter in the bottom of the baking dish using an offset spatula or knife.
Layer on the cream cheese mixture on top of this, again using the offest spatula or knife to ensure you get an even layer.
Finally layer on the remaining blondie batter and smooth evenly.
Bake in the preheated oven for 35 minutes. Some of the cream cheese will bubble over the sides, but that's okay. I think it gives the blondies an interesting look and makes them more delicious.
Let the blondies cool on a rack for an hour. Then refrigerate for at least four hours so they become completely firm. Lift the blondies out of the pan and on a chopping board using the parchment paper handles.
If some of the cream cheese is sticking to the parchment just use a knife to cut it out for a cleaner look. Cut the refrigerated blondies into squares and enjoy!