Heat oven to 350°F (175°C). Line the bottom and sides of a 9×13-inch cake pan with parchment, and coat it lightly with nonstick cooking spray.

Make the meringue: In a large bowl, beat the egg whites with ¼ teaspoon salt on medium/low speed until they begin to thicken. Increase speed to medium, add half the sugar, and continue to whip until glossy and stiff peaks form.

Make the cake: In a second bowl, beat the butter with the remaining sugar, salt, vanilla, and lemon zest until light and fluffy. Add egg yolks and beat to combine. Add baking powder, milk, and flour, and beat until smooth.

Bake the cake: Spoon the cake batter into the prepared pan and spread it into an even layer. Dollop the meringue on top and spread gently. Bake for 20-30 minutes until a toothpick comes out clean.

Cool the cake in the pan for 10 minutes, then transfer to a cooling rack.

Finish cake components: Combine strawberries, 1 tablespoon sugar, and lemon juice in a bowl. In another bowl, beat heavy cream, crème fraîche, remaining sugar, and vanilla until soft peaks form.

Assemble the cake: Cut the cooled cake in half lengthwise. Place one half on a plate, swirl with half the whipped cream, and scatter half the berries. Top with the second half, remaining cream, and berries. Garnish with mint leaves and/or powdered sugar.

To serve: Store in the fridge until needed. Cut into slices to serve. Leftovers keep in the fridge for 4 days.