Preheat oven to 350 degrees.
In a mixer fitted with a whisk attachment (or using a hand mixer), whip the egg whites, cream of tartar and salt in a clean, dry bowl until foamy. Add the granulated sugar, cornstarch, vinegar, and vanilla and continue whipping until stiff, smooth and glossy, about 8 minutes more. On a sheet of parchment paper cut to fit a sheet pan, use a pencil to draw or trace a circle 9-inches in diameter. Line the sheet pan with the parchment, pencil side down (you should still be able to see the circle). Spoon the egg whites into the circle, using the back of the spoon to smooth the top and sides of the disk. Bake in the center of the oven for 10 minutes, then reduce the heat to 300 degrees and bake until the meringue has puffed up and cracked on the top and the surface is lightly browned to the color of cafe au lait, about 45 minutes more. Turn off the oven, prop the oven door open, and let the pavlova cool in the oven at least 30 minutes, to room temperature. This ensures a gradual cooling, which protects the delicate meringue.
Whip the cream and brown sugar together until stiff. Spoon it in the center of the cooled pavlova and spread out to within 1/2-inch of the edge. Arrange the slices of kiwi around the edge. Arrange the slices of strawberry in the middle. To serve, slice into wedges with a serrated knife.