Place an oven rack in the center of the oven.

Preheat the oven to 200 degrees F (93 degrees C).

Line a baking sheet with parchment paper.

Set the prepared baking sheet aside.

In a stand mixer fitted with the whisk attachment, beat the egg whites until thick, approximately 2 minutes.

With the mixer on medium-high speed, gradually add the superfine baker's sugar, about 1 tablespoon at a time.

Add the sea salt, cream of tartar, and lemon zest.

Increase the mixer speed to high and beat until the meringue mixture holds stiff peaks, around 3 to 4 minutes.

Drop 8 (1/2) cupfuls of the meringue mixture onto the prepared baking sheet, spacing them about 2 inches apart.

Using the back of a spoon, make a 1 1/2-inch diameter well in the center of each meringue.

Bake in the preheated oven for 2 hours.

Turn off the oven and allow the meringues to cool completely in the oven for another 2 hours.

Store the baked pavlovas airtight in a plastic container for up to 1 week.

In a small bowl, gently toss together the fresh raspberries, blackberries or blueberries, sugar, and fresh lemon juice.

Refrigerate the berry mixture for at least 1 hour to allow the flavors to meld.

In a separate small bowl, mix together the mascarpone cheese, sugar, and pure vanilla extract until smooth and creamy.

To assemble, place the meringues on individual serving plates.

Spoon a dollop of the mascarpone cream into the well of each meringue.

Top with the marinated berries and serve immediately.