Place the flour, diced butter, and salt in a mixer, and mix until fine crumbs form. Add the water and continue mixing until the dough is smooth and uniform. Roll out the dough between two sheets of parchment paper to a thickness of 2 mm, then chill in the freezer for 10 minutes.

Remove the dough from the freezer, peel off the parchment paper, and trim to fit the baking pan. Reserve any excess dough in the freezer until needed.

Slowly sauté the onions with butter until caramelized.

Preheat the oven to 355°F (180°C) on convection mode.

In a bowl, mix the eggs with cream. Add the caramelized onions, cheese, salt, and pepper. Pour 2/3 of the mixture into the prepared dough in the pan. Layer with sweet potatoes, then pour over the remaining mixture. Top with another layer of sweet potatoes.

Bake for 35-40 minutes until set and golden.

Remove from the oven, cool slightly, and enjoy!