Step 1: Preheat Oven

1. Preheat your oven to 350°F (175°C).

Step 2: Prepare the Tart Crust

1. In a mixing bowl, combine the flour, powdered sugar, and salt.
2. Add the cold butter cubes and use a pastry cutter or your fingers to mix until the mixture resembles coarse crumbs.
3. Stir in the egg yolk and enough ice water to form a dough. Be careful not to overmix.
4. Form the dough into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes.
5. On a floured surface, roll out the chilled dough to fit a tart pan. Press the dough into the pan and trim any excess.

Step 3: Pre-bake the Tart Shell

1. Prick the bottom of the tart shell with a fork and bake for 15 minutes or until lightly golden. Remove from the oven and let cool.

Step 4: Make the Caramel Filling

1. In a medium saucepan over medium heat, melt the sugar until it turns a deep amber color, stirring occasionally.
2. Once melted, carefully add the cubed butter and stir until fully melted.
3. Remove from heat and slowly whisk in the heavy cream, vanilla extract, and salt until smooth. Let the caramel cool slightly.

Step 5: Assemble the Tart

1. Pour the caramel filling into the pre-baked tart shell, spreading it evenly.
2. In a bowl, mix the chopped nuts, granola, and caramel sauce until well combined. Sprinkle this mixture evenly over the caramel layer.

Step 6: Bake

1. Return the tart to the oven and bake for an additional 10–15 minutes, or until the topping is golden and the caramel is bubbling slightly.
2. Remove from the oven and let cool completely at room temperature. Refrigerate for at least 1 hour before serving.

Step 7: Serve

1. Slice the tart and serve chilled or at room temperature.