In a medium saucepan, combine the brown sugar, dark corn syrup, dark rum, and butter. Place over medium heat and cook, stirring constantly, until the mixture comes to a full boil. Allow it to boil for 2 minutes while stirring to prevent scorching. Remove the pan from the heat and let the mixture cool while the cheesecake continues baking.
In a separate bowl, whisk together the eggs, salt, and heavy cream until smooth. Set this mixture aside until the sugar syrup has cooled slightly.
After the cheesecake has baked for 40 minutes, carefully take it out of the oven. Slowly whisk the egg and cream mixture into the cooled sugar syrup until everything is fully combined and glossy. Stir in the chopped pecans, making sure they are evenly coated.
Using a spoon, gently distribute the pecan topping over the surface of the partially baked cheesecake. Start by spooning the pecans themselves over the top, then add just enough of the syrup to fill the crust without going above the crust line. Keeping the topping contained within the crust helps prevent it from seeping underneath and softening the crust or gluing the springform ring to the base.
Return the pan to the oven and bake for an additional 40–50 minutes, or until the pecan topping is golden brown and crisp on top. If you notice the edges of the pecan layer browning too quickly, tent them loosely with foil to prevent over-browning.
Transfer the cheesecake to a wire rack and let it cool completely at room temperature. Once cooled, cover the pan and refrigerate for at least 4 hours, or overnight, to allow the cheesecake to fully set.