1-First, preheat the oven to 350°F (177°C) and line a square pan with parchment paper, leaving an overhang for easy removal. Pulse the 9 graham crackers in a food processor until finely ground, then add the melted butter and ground cinnamon, pulsing again until moistened. Press this mixture firmly into the bottom of the pan and bake for about 10 minutes until fragrant, then let it cool completely. Next, reduce the oven temperature to 325°F (163°C) to prepare for the filling.

2-In a large bowl, beat the cream cheese, granulated sugar, and caramel sauce until smooth, making sure to scrape the sides regularly for an even mix. Add the sour cream or plain yogurt, then incorporate the eggs one at a time, mixing well after each addition to keep the batter creamy. Stir in the vanilla extract and fine sea salt, being careful not to overmix. Spread the batter evenly over the cooled crust and bake at 325°F for 40 to 45 minutes until the center is just set and the edges are puffed and slightly cracked.

3-After baking, turn off the oven, leave the door ajar, and let the cheesecake cool inside for 30 minutes. Then, move it to a wire rack to cool completely. Heat the caramel sauce for the topping until melted and spread it evenly over the cooled cheesecake. Refrigerate the bars for about 4 hours or overnight until thoroughly chilled. Before serving, sprinkle with flaky sea salt if desired, and slice with a hot knife for clean cuts just as the tips suggest for best results.