In a medium bowl, whisk together flour, cornstarch, baking powder, and salt to combine the dry ingredients evenly. In a separate large bowl, cream together the softened butter and sugar until light and fluffy, about 2-3 minutes—this incorporates air and creates a tender crust. Beat in the egg, milk, and vanilla extract until fully incorporated. Gently fold the dry ingredient mixture into the wet ingredients until just combined; don't overmix. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes to make it easier to roll and to develop flavor.

Preheat your oven to 350°F. Line a 12-inch round pizza pan or 13x9 inch baking sheet with parchment paper. Remove the chilled dough from the refrigerator and roll it out to about 1/4 inch thickness directly on the prepared pan, pressing it evenly to the edges. Bake for 20-25 minutes until the crust is light golden brown and set but not too dark. Remove from the oven and let cool completely on the pan—this prevents the marshmallow layer from melting.

While the crust cools, combine the marshmallow creme, softened cream cheese, vanilla extract, and lemon zest in a large bowl. Beat together until smooth and spreadable, about 1-2 minutes. I find that slightly softening the cream cheese at room temperature for 10 minutes makes this layer much easier to spread evenly without tearing the delicate crust beneath.

Once the crust is completely cooled, spread the marshmallow-cream cheese mixture evenly across the entire surface, leaving about 1/2 inch from the edges. Place the assembled pizza in the refrigerator for 15-20 minutes to set the topping and make it easier to add the fresh fruit without shifting.

While the topping sets, prepare all your fresh fruit: hull and slice the strawberries, peel and slice the kiwi, cut the pineapple into bite-sized chunks, and halve the grapes. In a small saucepan, gently warm the apricot preserves with the lemon juice over low heat, stirring until smooth, then strain through a fine mesh sieve to remove any lumps. I like to use a pastry brush to apply this glaze because it gives you the most control and creates an even, professional-looking shine.

Remove the pizza from the refrigerator and arrange all the prepared fruit in an attractive pattern across the topping—I recommend starting with larger pieces like strawberry and kiwi slices around the perimeter, then filling in with smaller berries and fruit pieces in the center. Brush or lightly drizzle the warm apricot glaze evenly over all the fruit to seal it and add shine. Garnish with fresh mint sprigs if desired. Refrigerate for at least 30 minutes before serving to allow everything to set together.