Preheat the oven to 350°F (180°C).
In a mixing bowl, combine the egg, sugar, and lemon zest. Mix for 2 to 3 minutes until well blended.
Add the heavy cream and mix again.
Add the flour and baking powder. Mix until smooth.
Pour the batter into a 10x10 inch (25x25 cm) springform pan lined with parchment paper.
Spread the batter evenly. Bake for 10 minutes. Let the cake cool in the pan.

Place the heavy cream in the freezer for 15 minutes along with the beaters. Then, using a mixer, whip the cold cream, mascarpone, and powdered sugar together.
Beat for about 2 1/2 minutes or longer, until stiff peaks form. Watch carefully so the cream doesn't turn to butter.
Add yellow food coloring to the whipped cream if desired.

Cloud cake without mascarpone.

In a mixing bowl, beat the egg whites and powdered sugar together for 10 minutes over a double boiler at 140°F (60°C), until stiff peaks form. Pipe the meringue over the lemon mousse using a piping bag.

Here, I used a kitchen torch to brown the meringue.

Absolutely delicious 😋

Enjoy! 😋