Preheat your oven to 350°F (175°C) and lightly spray a 13 x 9 x 2-inch pan with nonstick spray. In a mixing bowl, combine graham cracker crumbs, sugar, and cinnamon. Pour in the melted butter and mix well. Press this mixture into the bottom of the prepared pan, ensuring it's tightly packed. Bake for 10 minutes until golden brown, then let it cool completely.

In a food processor, blend the softened cream cheese and sugar until creamy. Gradually add in the dulce de leche, mixing until fully incorporated. Add the eggs one at a time, blending briefly after each addition. Add vanilla extract and mix until smooth. Carefully spread this filling over the cooled crust.

Place the pan in the preheated oven and bake for about 38 minutes. The edges should be set and the center should have a gentle wiggle. Once baked, cool the bars completely at room temperature.

In a microwave-safe bowl, combine the remaining dulce de leche with heavy cream. Heat in 10-second intervals, stirring until melted and smooth. Pour this topping over the cooled cheesecake filling, spreading it evenly. Refrigerate for about 1 hour to set and chill.

Once chilled, slice into 24 bars for serving. Just before serving, sprinkle a pinch of Fleur de Sel over each bar to enhance the dulce de leche flavor.