Preheat your oven to 375°F (190°C) for a perfectly baked crust.

In a large mixing bowl, combine the flour, sugar, and salt. Cut in the cold butter until the mixture resembles coarse crumbs. Stir in the egg yolk and add enough cold water to form the dough.

Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.

On a floured surface, roll out the dough to fit a 9-inch tart pan. Place it into the pan, prick the bottom, and cover with parchment paper and pie weights. Bake for 15 minutes until lightly golden.

While the crust is baking, combine the chopped rhubarb and sugar in a bowl and let sit for 10 minutes.

In another bowl, whisk together the cream, eggs, vanilla extract, and cornstarch until smooth.

Gently fold the rhubarb mixture into the cream mixture.

Pour the filling into the pre-baked crust and spread it evenly.

Bake for an additional 30-40 minutes until the edges are set and the center is slightly jiggly but thick enough to coat a spoon.

Allow the tart to cool for at least 15 minutes before slicing. Serve warm or at room temperature.