In a bowl, mix flour and salt. Cut in butter until mixture resembles coarse crumbs. Stir in cold water until dough forms. Wrap in plastic and refrigerate for 30 minutes.

In a skillet, heat olive oil over medium heat. Add sliced Vidalia onions and cook, stirring occasionally, until caramelized, about 20 minutes.

Preheat oven to 375°F (190°C). Roll out the chilled dough and fit it into a tart pan. In a bowl, whisk together cream, eggs, pepper, and nutmeg. Stir in caramelized onions and cheese. Pour mixture into the crust.

Bake in preheated oven for 30 minutes or until the filling is set and the top is golden brown. Let cool slightly before serving.