For the meringue; In a mixing bowl, add powdered sugar, cornstarch and cream of tartar; whisk well and set aside.
In the bowl of a stand mixer, add egg whites and with the whisk attachment, process on high speed until soft peaks form, about 4 minutes.
Add 1/3 powdered sugar mixture and process until completely incorporated, about 1 minute. Add1/3 sugar mixture at a time, whisking well after each addition. Clean the sides of the bowl and process for 30 seconds. Scoop some meringue and invert it; if it holds its shape, is thick and glossy, it means it’s ready. Add vanilla extract and process once again for 1 minute.
As a reference for a perfect circle, place the bottom of an 8-inch tart pan on a baking sheet lined with a silicone mat before covering it with some parchment paper. Scoop the meringue on the paper, forming a circle using the outline of the tart pan bottom; when shaped, remove the 8-inch bottom pan. Bring up the outside edge to 2 inches high with an indentation in the center for the toppings after the meringue is cooked. Make peaks around the edge with the tip of the spatula.
When ready to bake, reduce the heat to 215ºF and gently place the meringue in the oven. Carefully close the oven door to prevent it from deflating and bake for 1:30 hours.
When the time is up, turn off the heat and leave the Pavlova in the oven, undisturbed, for 24 hours.
The next day, carefully transfer the Pavlova to a cake stand and slide a thin spatula under to release it from the parchment paper; remove the paper and discard it.
In the bowl of a stand mixer with the whisk attachment, add cold heavy cream; process on high speed for 2 minutes. Add powdered sugar and vanilla extract; whisk until stiff peaks form.
To prevent it from caving in, gently spoon the whipped cream onto the center, covering any cracks or imperfections. Top with fresh fruits of your choice.