Prepare the tart crust by mixing gluten-free flour, powdered sugar, and salt. Add softened butter and mix until crumbly. Stir in egg yolk and cold water, then press into a tart pan and prick the bottom. Bake at 350°F for 15-20 minutes until golden. Let cool completely.
Make the whipped cream by whipping heavy cream, granulated sugar, and vanilla extract until soft peaks form. Set aside.
Spread the whipped cream evenly over the cooled tart shell.
Arrange mixed fresh fruit on top of the whipped cream in a decorative pattern. Optionally, prepare a glaze by heating apricot jam and water, then brush over the fruit.
Chill the tart in the refrigerator for at least 30 minutes before serving.