Preheat oven to 325°F. Line a 9x9-inch baking pan with parchment paper, leaving two sides long to create a sling.
Combine graham cracker crumbs, butter, and ¼ teaspoon of baking salt. Press mixture evenly into bottom of prepared pan. Bake until lightly golden-brown, about 8-10 minutes. Remove and allow crust to cool completely.
Meanwhile, beat cream cheese, sugar and remaining baking salt together until smooth. Add eggs one at a time, mixing well after each addition, until combined. Mix in sour cream, flour, vanilla, and orange zest until smooth.
Transfer batter to cooled crust. Drizzle marmalade over batter and swirl using a toothpick or skewer.
Bake until edges are set and center is slightly jiggly, about 40-45 minutes.
Allow bars to cool completely in pan, then refrigerate for at least 4 hours or overnight to set.
Once chilled, lift cheesecake out of pan and cut into bars. Serve and enjoy!