Peel and chop the fresh peaches, then blend until smooth in a food processor. In a saucepan, combine the peach puree with granulated sugar, cornstarch, and lemon juice. Cook for 5-7 minutes until thickened, cool completely.

Preheat the oven to 350°F (175°C). Butter a 9-inch square baking pan and line it with parchment paper.

In a food processor, pulse together vanilla wafer crumbs and pecans. Add melted butter and sea salt, mixing until resembling wet sand. Press into the bottom of the prepared pan and bake for 8-10 minutes until lightly golden.

Lower the oven temperature to 325°F (160°C). Beat cream cheese, crème fraîche, sugar, and flour in a large bowl until smooth. Eliminate lumps.

Incorporate eggs one at a time, mixing well after each. Blend in lemon juice, vanilla paste, and salt until creamy.

Pour cheesecake filling over the cooled crust, spreading evenly. Drop dollops of cooled peach puree over the filling, swirling with a toothpick for a marbled effect.

Bake at 325°F (160°C) for 25-35 minutes until center is slightly jiggly but set. Let cool at room temperature for about an hour.

Refrigerate the bars for at least 2 hours until fully chilled. Lift out using parchment overhang and slice into squares for serving.