Preheat your oven to 350°F (175°C). Prepare a 9-inch springform pan by spraying it with cooking spray, lining the base with parchment paper, and wrapping the outside with heavy-duty aluminum foil.

For the crust, combine the graham cracker crumbs, chopped pecans, sugar, cinnamon, and salt in a bowl. Stir in the melted butter until the mixture resembles wet sand.

Press the crust mixture into the bottom and up the sides of the prepared springform pan using a flat-bottomed measuring cup or your fingers to ensure even distribution.

Bake in the preheated oven on the center rack for about 10 minutes, until lightly golden and aromatic. Remove from the oven and allow to cool on a wire rack for 15 minutes. Lower the oven temperature to 325°F (165°C) and adjust the rack to the lower third position.

While the crust cools, prepare the cheesecake filling. In a food processor, blend the cream cheese and brown sugar until smooth and lump-free, about 45 seconds. Gradually add the eggs, one at a time, pulsing once after each addition. Then, add the sour cream, flour, vanilla, cinnamon, and salt, pulsing 2-3 times to combine. Pour the batter into the cooled crust.

Bake the cheesecake for 45-50 minutes at 325°F (165°C) on the lower rack until the center jiggles slightly. Turn off the oven, leave the door ajar, and let the cheesecake rest in the oven for an hour. Once cooled, run a knife around the edge of the pan to loosen the crust, discard the foil, and cover the cheesecake. Refrigerate for at least 6 hours or overnight.

To prepare the pecan pie topping, set a medium nonstick saucepan over low heat and sprinkle the sugar evenly in the pan. Let it warm undisturbed for about 2 minutes. Add the water and stir continuously until the sugar fully melts, about 45 seconds. Stir in the butter, continuing to stir until fully incorporated, about 30 seconds.

Raise the heat to medium and add the heavy cream, rum, cinnamon, and vanilla. Stir constantly until the mixture thickens slightly, about 2 minutes. Add the toasted pecans, ensuring they are well-coated with the syrup, then remove from heat. Let the topping cool to room temperature and thicken, about 30 minutes.

Once the cheesecake has fully chilled, carefully remove it from the springform pan and place it onto a serving platter. Generously top with the cooled pecan pie topping. Serve immediately or allow the cheesecake to soften for 15 minutes before serving.