Mix the almond flour, powdered allulose, and salt. Stir in the melted butter, then press the crust into a 9-inch springform pan and chill.
Add the blueberries, lemon juice, and powdered allulose to a small saucepan. Cook over medium-low heat for 4 to 5 minutes, mashing the berries until juicy.
Whisk the egg yolks in a bowl, then slowly whisk in a few spoonfuls of the warm blueberry mixture. Return everything to the saucepan and cook for 2 to 3 minutes, stirring constantly, until thickened.
Remove from the heat and stir in the butter until smooth. Cool the blueberry lemon curd completely.
Beat the cream cheese, powdered allulose, sour cream, vanilla extract, and lemon zest until smooth.
Whip the cold heavy cream to firm peaks, then fold it into the cream cheese filling. Spread the filling over the crust and spoon the cooled curd over the top.