To make the crust place the butter into a large saucepot and heat over high heat. Stir often. After about 3 minutes, the butter will start to froth up and brown flecks will appear. Keep whisking and once the butter is medium brown, remove from the heat and stir in the allulose and milk powder. Allow to cool for a little bit, but while it is still liquid, pour into a parchment lined (otherwise it will stick) 9 by 11 casserole dish. Place in the fridge to set.
While the crust chills, make the filling. Place the cream cheese into a large bowl and stir well until there are no clumps. Add the sour cream, lemon juice, powdered allulose and stir well.
Place 2 tablespoons heavy cream into a small bowl and add the gelatin. Stir well to combine, then heat in 15 second increments until the gelatin has melted. Use a spatula to combine the gelatin mixture into the cream cheese mixture.
Place the rest of the cream into a large bowl and use a hand mixture until stiff peaks form. Stir the whipped cream into the cream cheese mixture. Add the salt and stir well. Taste and adjust sweetness to your liking.
Pour the cream cheese filling onto the chilled crust. Place back into the fridge for 3-4 hours or until set.
Store extras in an airtight container in the fridge for up to 7 days.