In a mixing bowl, combine flour and sugar. Cut in the butter until the mixture resembles coarse crumbs.

Stir in the egg yolk and enough ice water to form a dough. Shape into a disk, wrap in plastic, and refrigerate for 30 minutes.

Preheat the oven to 375°F (190°C). Roll out the dough and fit it into a 9-inch tart pan. Prick the bottom with a fork.

Bake the crust for 15 minutes or until lightly golden. Remove from oven and let cool.

In a saucepan, combine chopped rhubarb and sugar. Cook over medium heat until the rhubarb is tender, about 5-7 minutes.

In a bowl, whisk together heavy cream, eggs, vanilla extract, and salt.

Spread the rhubarb mixture evenly over the cooled tart crust. Pour the custard mixture over the rhubarb.

Bake for 25-30 minutes or until the custard is set and lightly browned. Let cool before serving.