Prep the pan: Heat oven to 325°F (163°C). Line the bottom of a 9-inch springform pan with parchment.
Lightly grease the sides.
Make the crust: Mix crumbs, melted butter, sugar, and salt. Press evenly into the bottom and 1 inch up the sides. Bake 8–10 minutes.
Cool while you make the filling.
Beat the cream cheese: In a large bowl, beat cream cheese on medium until smooth, about 2 minutes. Add granulated sugar and beat until fluffy, scraping the bowl.
Add flavor: Beat in sour cream, vanilla, orange zest, orange juice, and gelatin powder (if using). Mix just until combined and smooth.
Add eggs: Beat in eggs one at a time on low, just until incorporated.
Do not overmix.
Whip the cream: In a separate bowl, whip heavy cream with powdered sugar to medium peaks. Gently fold into the cheesecake batter until no streaks remain.
Assemble: Pour filling into the cooled crust. For the swirl, stir marmalade with water, dot small spoonfuls on top, and drag a toothpick through to create swirls.
Add food coloring if desired.
Bake: Place the pan on the center rack. Bake 45–55 minutes. The edges should be set and the center slightly wobbly, like Jell-O.
Topping: Whisk sour cream, powdered sugar, and vanilla.
Gently spread over the hot cheesecake. Return to oven for 5 minutes.
Cool slowly: Turn off the oven, crack the door, and let the cheesecake sit 30 minutes. Move to a rack and cool to room temp.
Chill: Cover and refrigerate at least 6 hours, ideally overnight.
Release the springform and slice with a warm, clean knife.