Preheat oven to 225°F. Place a piece of parchment paper on a sheet pan. Place a 8–9 inch cake pan tin upside down on top of the parchment paper, and draw a circle around the tin. Flip the parchment paper over (the circle should still be visible).
Place the egg whites in the bowl of a stand mixer. Beat on high until the egg whites are stiff but not dry. Add the sugar, ¼ cup at a time, beating well after each addition. Beat until thick and glossy. Add the lemon zest, cream of tartar, and pinch of salt. Beat gently to combine.
Pour the egg white mixture onto the parchment paper. Starting in the middle, spread the mixture out toward the edges of the circle. The edges should be slightly higher than the middle.
Bake for 1 hour and 45 minutes. Place the pavlova and parchment paper on a cooling rack and cool completely. When cool, gently peel the parchment paper away from the pavlova.
Place the whipping cream in the bowl of a stand mixer. Beat on high until soft peaks form. Add the powdered sugar, Greek yogurt, and lemon zest. Beat until whipped cream holds it shape, being careful not to overmix it.
Spoon the whipped cream on top of the pavlova. Decorate the top with the fruit, whether in a flag pattern or mixed together. Serve immediately.
Notes
Separate the egg whites carefully—any trace of yolk may cause the whites not to whip up properly. If you get any yolk in them, save them for another use and start again. Sour cream can be substituted for the Greek yogurt. It gives the whipped cream a nice tang that complements the sweetness of the pavlova nicely!