Preheat your oven to 350°F (175°C) and prepare a 9-inch springform pan by greasing it or lining the bottom with parchment paper.

In a food processor, combine all-purpose flour, powdered sugar, unsalted butter, and salt. Pulse until resembling coarse crumbs, then press evenly into the bottom of the springform pan. Bake for 15-18 minutes until golden brown and let cool on a wire rack.

Sprinkle gelatin over cold water in a small bowl and let bloom for about 5 minutes. Set it aside.

Warm fresh lemon juice in a small saucepan over low heat, stir in bloomed gelatin until dissolved, and set aside to cool. In a mixing bowl, whip heavy cream, granulated sugar, and lemon zest until stiff peaks form. Beat cream cheese until smooth, fold in cooled lemon mixture, and combine with whipped cream.

For the blueberry compote, combine fresh blueberries, granulated sugar, and lemon juice in a saucepan over medium heat. Cook for about 5-7 minutes until softened, then cool to room temperature.

Spread an even layer of lemon mousse over the cooled crust, followed by a layer of blueberry compote. Repeat layers, finishing with a dollop of blueberry compote on top.

Cover with plastic wrap and refrigerate for at least 4 hours until set.

Run a knife around the edge of the springform pan to loosen the cake. Remove the sides gently, slice, and serve chilled. Garnish with fresh blueberries or whipped cream if desired.