Preheat oven to 350°F (175°C). Line a 12-inch pizza pan or a large baking sheet with parchment paper.
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy. Beat in the egg and vanilla extract.
In a separate bowl, whisk together the flour and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Press the dough evenly onto the prepared pizza pan to form a crust.
Bake for 15-20 minutes, or until golden brown and cooked through. Let cool completely on a wire rack.
While the crust cools, prepare the cream cheese frosting. In a medium bowl, beat together the softened cream cheese and butter until smooth. Gradually beat in the powdered sugar and vanilla extract until well combined and fluffy.
Spread the cream cheese frosting evenly over the cooled crust.
Arrange the fresh fruit on top of the frosting to create the flag design. Use blueberries for the stars in a corner, and arrange strawberries and raspberries in stripes.
Chill for at least 30 minutes before slicing and serving.
Notes
This fruit pizza is best enjoyed the same day it's made. You can substitute other fruits based on seasonality and preference.