Prepare the crust: Preheat oven to 350°F (175°C). In a medium bowl, combine graham cracker crumbs, sugar, melted butter, and salt. Press the mixture firmly into the bottom and sides of a 9-inch springform pan. Bake for 10 minutes, then let cool completely.
Whip up the key lime filling: In a large bowl, beat cream cheese and sugar until light and fluffy. Add eggs one at a time, beating well after each addition. Stir in key lime juice, sour cream, and vanilla extract until smooth.
Mango magic: In a small saucepan, whisk together mango puree, sugar, and cornstarch. Heat over medium heat, stirring constantly, until thickened and bubbly. Let cool slightly.
Swirl and bake: Pour the key lime filling into the cooled crust. Dollop spoonfuls of mango puree on top, then gently swirl with a knife to create a marbled effect. Bake for 35-40 minutes, or until the center is slightly jiggly.
Chill and thrill: Let the cheesecake cool completely on a wire rack, then cover and refrigerate for at least 4 hours, preferably overnight.
Top it off and serve: Before serving, whip up some fresh cream and garnish the cheesecake with dollops, slices of fresh mango, and a sprinkle of lime zest for an extra citrusy zing.