Preheat your oven to 250°F and line a large baking sheet with parchment paper. I like to trace a circle on the parchment about 10 inches wide—this gives you a visual guide. It keeps the meringue from spreading too thin while baking.

Add your 4 egg whites to a super clean mixing bowl (seriously, even a tiny drop of grease ruins everything). Beat them on high speed until soft peaks form, which takes about 2 minutes. You'll see them get fluffy and white, and when you pull the beaters up, they'll fold back over.

Gradually sprinkle in the caster sugar one tablespoon at a time while the mixer runs. This takes about 5-7 minutes total. Keep beating until you get stiff, glossy peaks that hold their shape completely—when you turn the bowl sideways, nothing moves.

Fold in the cornstarch, white vinegar, and lemon zest gently using a spatula. Don't use the mixer for this step—just fold it in with 10-12 gentle strokes. You want to keep all that air you just whipped in.

Spoon the meringue onto your parchment circle and create a little well in the center with the back of a spoon. This creates a bowl-like shape that's perfect for catching cream and berries later. Bake for 1 hour and 20 minutes at 250°F, until it's pale and crispy outside.

Turn off the oven and crack the door open about 3 inches. Let it cool in there for at least 30 minutes—this prevents cracking. Don't panic if it looks slightly darker than you expected. That's totally normal and actually means it's crispy.

While the meringue cools, whip your heavy cream with powdered sugar and lemon juice until soft peaks form—about 2 minutes with a mixer. Toss your strawberries and blueberries together gently in a bowl.

Right before serving, slide the meringue onto your serving plate and pile that whipped cream into the center. Top with your mixed berries and that gorgeous lemon zest. The whole thing comes together in literally 5 minutes, and everyone will think you're a dessert wizard.