- 2 cups water
- 2 cups sugar
- 1 vanilla bean, split lengthwise
- 9 ounces kumquats (about 25 medium), thinly sliced crosswise, seeds removed
- 2 cups vanilla wafer cookie crumbs (made from about 9 ounces cookies, finely ground in processor)
- 1/3 cup (packed) golden brown sugar
- 6 to 7 tablespoons unsalted butter, melted
- 1 cup fresh orange juice
- 1 cup sugar, divided
- 2 tablespoons finely grated orange peel
- 4 8-ounce packages cream cheese, room temperature
- 1 cup sour cream
- 3 tablespoons all purpose flour
- 1/4 teaspoon salt
- 5 large eggs, room temperature
- Combine water and sugar in medium saucepan. Scrape in seeds from vanilla bean; add bean. Stir over medium heat until sugar dissolves. Add kumquats; reduce heat. Simmer until kumquat slices are translucent, about 25 minutes. Remove from heat; cool kumquats in syrup. Strain kumquats, reserving syrup. Combine kumquats and 1/4 cup syrup in small bowl. Return remaining syrup to same saucepan; boil until reduced to 1 1/4 cups, about 8 minutes. DO AHEAD: Can be made 2 days ahead. Cover separately and chill.
- Position rack in center of oven and preheat to 350°F. Combine cookie crumbs and brown sugar in medium bowl; add 6 tablespoons melted butter and stir until crumbs feel moist when pressed together with fingertips, adding remaining 1 tablespoon melted butter if mixture is dry. Press crumb mixture evenly onto bottom and 1 inch up sides of 9-inch-diameter springform pan with 2 3/4-inch-high sides. Bake crust until set and edges are golden brown, about 20 minutes. Cool crust in pan on rack. Maintain oven temperature.
- Wrap 4 layers of heavy-duty foil tightly around outside of pan with crust to make pan waterproof.
- Combine orange juice, 1/4 cup sugar, and orange peel in small saucepan. Bring to boil, stirring until sugar dissolves. Reduce heat. Simmer until mixture is reduced to 3/4 cup, about 10 minutes. Chill until cool.
- Meanwhile, using electric mixer, beat cream cheese and remaining 3/4 cup sugar in large bowl until smooth. Mix in sour cream, flour, and salt. Beat in eggs 1 at a time. Mix in cooled orange juice mixture. Pour filling into crust; place springform pan in large roasting pan. Pour enough hot water into roasting pan to come halfway up sides of springform pan.
- Bake cake until just set in center, about 1 hour 35 minutes. Remove cake from roasting pan; remove foil. Place cake directly in refrigerator and chill overnight. Arrange kumquat slices atop cake, covering completely. DO AHEAD: Can be made 1 day ahead. Tent cake with foil and refrigerate.
- Remove pan sides; place cake on platter. Cut cake into wedges; drizzle some kumquat syrup over and serve.
- The KUMQUAT SYRUP is perfect with the cake—but don't stop there. It's also yummy drizzled over vanilla or coffee ice cream or in a cup of tea, a glass of club soda, or even a vodka Martini.