Preheat the oven to 350°F (175°C). In a bowl, mix flour, butter, and powdered sugar until crumbly. Add egg yolk and mix until dough forms.

Press the dough into the tart pan evenly and prick the bottom with a fork. Bake for 15 minutes or until lightly golden.

In a bowl, whisk together orange juice, champagne, sugar, eggs, and orange zest until well combined.

Pour the filling into the baked crust and bake for an additional 15 minutes or until set.

Allow the tart to cool before slicing. Serve chilled or at room temperature.