Preheat the oven to 350°F (175°C). Grease a 9-inch springform pan with butter or cooking spray.

In a mixing bowl, combine all-purpose flour, powdered sugar, unsalted butter, and salt. Blend until coarse crumbs form, then press firmly into the bottom of the prepared springform pan.

Bake for 15 to 18 minutes until golden brown; cool completely.

Sprinkle gelatin powder over water in a small bowl and let sit for 5 minutes. Heat fresh lemon juice in a saucepan, stir in gelatin until dissolved, and let cool.

In another bowl, whip heavy cream, granulated sugar, and lemon zest until stiff peaks form.

Whip cream cheese until smooth. Add cooled gelatin mixture and combine, then gently fold in whipped cream.

Combine fresh blueberries, granulated sugar, and lemon juice in a saucepan, cook until berries soften, about 5-7 minutes. Cool.

Spread half the lemon mousse over the shortbread crust, layer half the blueberry compote, then repeat with remaining mousse and compote.

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

Run a knife around the pan edge to loosen, remove sides, slice, and serve chilled.