Preheat the oven to 350 degrees F (175 degrees C).
Combine flour, cream of tartar, baking soda, and salt in a medium bowl.
Cream butter and 3/4 cup sugar in a large bowl, then add the egg and mix well.
Stir in the dry ingredients until just blended and press the dough into a pizza pan.
Bake for 8 to 10 minutes until lightly browned, then cool.
Beat cream cheese, remaining sugar, and vanilla until light and fluffy.
Spread the cream cheese mixture evenly over the cooled crust.
Arrange blueberries, strawberries, and banana slices on top, then chill before serving.