Preheat your oven to 350°F (175°C). Prepare a 9×13-inch cake pan by lining the bottom and sides with parchment paper and lightly spraying it with nonstick cooking spray.

To make the meringue, in a large bowl using a stand mixer with a whisk attachment or a hand mixer, beat the egg whites with ¼ teaspoon of salt on medium-low speed until they start to thicken and appear satiny.

Increase the speed to medium and gradually add ¾ cup of sugar, allowing each addition to dissolve before adding more. Mix in ½ teaspoon of vanilla extract or paste and continue whipping until the egg whites are glossy and stiff peaks form.

In another bowl, beat the softened butter with the remaining ¾ cup of sugar, ¼ teaspoon of salt, the remaining ½ teaspoon of vanilla, and the lemon zest until the mixture is light and fluffy.

Add the egg yolks to the butter mixture and beat until well combined. Sprinkle the baking powder over the batter and mix thoroughly.

Pour in the milk and mix until combined. The batter may look curdled, but that's normal. Add the flour and beat until the mixture is smooth and well combined.

Spoon the cake batter into the prepared pan, spreading it into an even layer. Dollop the meringue mixture over the batter and gently spread it out.

Bake the cake for about 20 minutes, then check for doneness with a toothpick. If it comes out clean, the cake is done; if not, it may need an additional 5 to 10 minutes.

Once baked, let the cake cool in the pan for 10 minutes. Use the parchment to carefully lift the cake out and transfer it to a cooling rack to cool completely.

In a medium bowl, mix the strawberries with 1 tablespoon of sugar and lemon juice, then set aside to let them release their juices.

In a large, clean bowl, combine the heavy cream, crème fraîche, the remaining 1 tablespoon of sugar, and vanilla extract or paste. Beat until soft peaks form.

To assemble the cake, cut the cooled cake in half lengthwise to create two long rectangles. Carefully transfer the first half to a plate, spread half of the whipped cream on top, and scatter half of the strawberries over it.

Place the second half of the cake on top of the strawberries, then finish with the remaining whipped cream and strawberries. Drizzle any extra strawberry juices over the top.

If desired, garnish with mint leaves and a dusting of powdered sugar. Store the cake in the fridge until ready to serve, and cut into slices to enjoy. Leftovers can be kept in the fridge for up to 4 days.