In a food processor, add all the ingredients for the tart crust and pulse until everything is combined and forms a ball of dough off to the side of the processor. Wrap the dough in plastic wrap and refrigerate for at least 2 hours.

When the dough has chilled, preheat the oven to 350F and lightly grease a 9-inch tart pan. Set aside.

Roll out the dough over the floured surface and press into the tart pan. Dock with a fork and bake for 20 minutes until slightly golden brown at the edges of the tart pan. Cool on a wire rack when you make the filling.

In a tall saucepan, mix the sugar and water with your hands until all the sugar is like wet sand. Place over medium heat and do not stir, as this will cause the sugar to crystallize. As it melts and cooks, the sugar will turn into a gorgeous golden color and When it's a light golden color, you can carefully pour the measured cream over it. It is going to bubble like crazy, so stand back for a second and with a whisk at hand, stir and lower the heat. The sugar will stick to the whisk for a second then melt back. Remove from heat and keep stirring, adding the salt, butter, and vanilla. Set aside to cool down for 15 minutes.

When the caramel slightly thickens, place the walnuts in a single layer on the cooled tart shell and carefully pour the caramel over the walnuts, making sure to get it everywhere in the tart. Using a fork, carefully move around the walnuts to be sure every spot has caramel.

Chill the tart before serving to set the caramel and enjoy chilled!