Heat the oven to 180C / 350F and line 2 x 20cm cake tins with baking paper.
To make the cake: Put the cake mix in a bowl and pour in the lemonade mix until combined.
425 g cake mix box, 330 ml lemonade (soda can)
Divide the batter between the two cake tins and bake in the oven for 20-25 minutes and then, allow it to cool.
To make the frosting: In a mixing bowl, whisk heavy cream, lemon zest, powdered sugar and vanilla extract until stiff peak forms.
300 ml Heavy cream, ¼ cup powdered sugar, 1 teaspoon vanilla extract, 1 lemon zest
Assemble the cake: Place one cake on a serving plate, spread half of the frosting on top, and add the next layer and the rest of the frosting in an even layer.
Make swirls of whipped cream on the edges and sprinkle some lemon zest.
Notes
Do not over-whisk or overbeat your batter. This will make the cake dense, and you will lose all the moisture and fluffiness.
Make sure to use 20 cm cake tins for this recipe; using a bigger cake tin might make the cake too thin, while using a smaller cake tin might make the cake too thick.