Prepare the Crust : Preheat the oven to 350°F (175°C). Line a 9x13-inch baking dish with parchment paper and lightly coat with nonstick spray. In a mixing bowl, combine the finely ground graham crackers, 6 tablespoons of sugar, 1/4 teaspoon cinnamon, and melted butter. Mix until the crumbs are evenly moistened. Press the mixture firmly into the bottom of the prepared baking dish to form an even crust. Bake for 10 minutes, then set aside to cool.

Make the Cheesecake Filling : In a large bowl, beat the softened cream cheese and remaining 12 tablespoons of sugar using an electric mixer until smooth and creamy. Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract and heavy whipping cream until fully incorporated.

Assemble and Bake : Pour the cheesecake filling over the pre-baked crust, spreading it evenly. Drop dollops of 1/2 cup of dulce de leche on top of the cheesecake layer and swirl it gently with a knife for a marbled effect. Bake for 30-35 minutes, or until the center is set and slightly jiggles when shaken.

Cool and Add Topping : Let the cheesecake cool completely at room temperature, then refrigerate for at least 4 hours (preferably overnight). Before serving, spread the remaining dulce de leche evenly over the top. Sprinkle with fleur de sel for a hint of salty contrast.

Slice and Serve : Using a sharp knife, cut the chilled cheesecake into bars. Serve chilled and enjoy the creamy, caramelized goodness!