• Preheat the oven to 160° C/320° F (fan).

For the butter caramel:

• Heat a saucepan over medium-low heat, add the sugar in batches, and stir slowly with a wooden spoon until it turns into a dark caramel. Gradually pour in the heavy cream while continuously stirring.
• Allow the mixture to simmer for 8-10 minutes, then remove the saucepan from the heat. Add the cold butter and salt, stir well, and set aside to cool completely.

For the Crust:

• In a large bowl, combine the flour, salt, cold butter, powdered sugar, and baking powder. Wearing disposable gloves, start rubbing the butter into the flour with your hands until the mixture resembles crumbs.
• Add the egg yolk and knead until it forms a pliable dough (if it's too stiff, you can add a little water). Shape the dough into a disc, wrap it in plastic wrap, and refrigerate for 1 hour.
• Once chilled, take two sheets of parchment paper, flour them, and roll out the dough between them using a rolling pin. If the dough sticks, sprinkle a little more flour.
• Take a rectangular cake pan (30x12 cm or 12x5 inches), line the bottom with parchment paper, and press the dough into the bottom and sides of the pan. Make sure it sticks well and prick the surface of the dough with a fork.
• Place parchment paper over the dough and fill with beans to weigh it down, preventing the dough from puffing up while baking. Bake in the oven for 20 minutes.
• Remove the tart from the oven, remove the beans, brush the surface with the egg yolk diluted with a little water, and bake at 180° C/356° F (fan) until golden brown. Once ready, remove from the oven and let it cool completely.

For the ganache:

• In a saucepan, heat the cream until it just begins to boil. Turn off the heat, add the chocolate, and stir until completely melted. Set aside.

For the assembly:

• Carefully unmold the tart and place it on a serving plate. Pour the cooled caramel inside, followed by the ganache on top. Finish with a sprinkle of salt, chopped hazelnuts, and pomegranate seeds. Refrigerate for 2 hours before serving.
• Cut the tart into pieces and serve.