Preheat your oven to 325°F (165°C). Line an 8x8-inch or 9x9-inch metal baking pan with parchment paper, leaving an overhang on the sides for easy lifting. In a medium bowl, stir together graham cracker crumbs, brown sugar, melted butter, cinnamon, and salt until evenly moistened. Press firmly and evenly into the bottom of the pan. Bake for 10 minutes, then remove and set aside to cool slightly.

In a large mixing bowl with an electric hand mixer on medium-low speed, beat the softened cream cheese and granulated sugar for 2 minutes until creamy and free of lumps. Beat in the sour cream, pure vanilla extract, and flour. Add the eggs one at a time, mixing on low speed just until each egg is incorporated (avoid over-beating to prevent excess air bubbles).

Pour the cheesecake batter over the pre-baked crust and smooth the top with an offset spatula. Bake at 325°F for 30 to 35 minutes until the outer edges are puffed and set, but the center has a gentle, slight jiggle when tapped. Remove from the oven and cool completely at room temperature for 1 hour, then refrigerate for at least 2 hours to firm up.

In a medium heavy-bottomed saucepan over medium heat, melt 1/2 cup butter and 1/2 cup brown sugar together. Bring to a gentle bubbling boil, stirring constantly with a silicone spatula for 3 minutes until thickened and syrupy. Remove from heat and stir in heavy cream, toasted pecans, and flaky sea salt. Allow to cool for 5 to 7 minutes until warm and spoonable.

Pour the warm caramel pecan mixture evenly across the chilled cheesecake layer, spreading gently to the edges. Return to the refrigerator for 1 hour until the caramel layer sets into a glossy, sliceable crown. Lift the entire block out of the pan using parchment overhang. Using a sharp chef's knife dipped in warm water and wiped dry between cuts, slice into 16 neat bars. Garnish with a final sprinkle of flaky sea salt and serve!