Preheat the oven to 350°F (175°C).
In a large bowl, cream together 1 cup softened butter and 1/2 cup granulated sugar until light and fluffy.
Add 2 cups all-purpose flour and 1/4 teaspoon salt to the butter mixture and mix until just combined.
Stir in 1 teaspoon vanilla extract until incorporated.
Press the dough evenly into a 12-inch round pizza pan or baking sheet lined with parchment paper.
Bake the shortbread crust for 25 minutes or until the edges are lightly golden.
Remove from oven and allow the crust to cool completely in the pan on a wire rack.
While the crust cools, prepare the frosting by beating together 8 ounces softened cream cheese and 1/4 cup softened butter until smooth and creamy.
Add 1 cup powdered sugar and 1 teaspoon vanilla extract to the cream cheese mixture and beat until fully combined and fluffy.
Spread the cream cheese frosting evenly over the cooled shortbread crust.
Arrange the sliced strawberries, blueberries, kiwi, mandarin orange segments, and halved grapes decoratively on top of the frosting.
Refrigerate the fruit pizza for at least 30 minutes before slicing and serving to allow the frosting to set.