Preheat oven to 350°F (175°C) and grease a 9-inch springform pan; line bottom with parchment paper.
In a heatproof bowl, melt white chocolate with cream or milk over a double boiler until smooth; set aside to cool slightly.
In a large bowl, beat butter, sugar, and lemon zest until light and fluffy.
Add egg yolks one at a time, mixing well after each addition.
Stir in lemon extract, lemon juice (or limoncello), and the melted white chocolate mixture.
Gently fold in almond flour until fully incorporated; batter will be thick.
In a separate bowl, whip egg whites until soft peaks form, then fold gently into the batter.
Pour batter into the prepared pan and smooth the top with a spatula.
Bake for 35–40 minutes or until golden and a toothpick inserted in the center comes out clean.
Cool completely, then dust with powdered sugar before serving.