1. Preheat oven to 350°F (175°C)

2. Line a 9x13-inch (23x33 cm) baking dish with parchment paper leaving overhang for easy removal

3. Beat almond paste and sugar until smooth in a medium bowl then mix in most of the lemon zest reserving a pinch for garnish

4. Whip egg whites in a separate bowl until stiff peaks form

5. Gently fold egg whites into almond mixture until no streaks remain

6. Pour batter into prepared dish and bake 25 to 30 minutes until lightly golden

7. Cool cake completely in the dish

8. Melt white chocolate in a double boiler

9. Whip heavy cream until stiff peaks form

10. Fold whipped cream into melted white chocolate until smooth

11. Spread topping evenly over cooled cake

12. Sprinkle with reserved lemon zest and serve