Lemon Swirl Cheesecake

Crust:
6 whole graham crackers (about 3 ounces)
1 cup slivered almonds*, toasted
3 tablespoons butter, melted
2 teaspoons lemon zest
Filling:
2 8-ounce packages cream cheese, softened
1/2 cup sugar
1/2 cup frozen lemonade** concentrate, thawed
2 teaspoons lemon zest
3/4 cup sour cream
2 large eggs
Topping:
1 cup sour cream, room temperature
1 11 1/4-ounce jar purchased lemon** curd
For Crust:
Position rack in center of oven and preheat to 350°F. In food processor, finely grind graham crackers. Add nuts; process until coarsely chopped. Drizzle in butter. Add lemon peel. Blend until combined. Press crumbs firmly onto bottom of 9-inch-diameter springform pan. Bake until crust is set, about 10 minutes. Cool.
For Filling:
Beat cream cheese, sugar, concentrate and zest until smooth. Beat in 3/4 cup sour cream. Add eggs 1 at a time, beat just until combined. Pour into crust. Bake until center (about the size of a quarter) moves only slightly when pan is shaken, about 50 minutes. Transfer to rack; cool 5 minutes.
For Topping:
Whisk 1 cup sour cream in small bowl until very smooth. Whisk lemon curd in another small bowl until very smooth. Run small sharp knife around sides of cake. Starting at outside of edge of cake, spoon small alternating dollops of sour cream and lemon curd side by side in concentric circles atop warm cake, covering cake completely. Gently shake pan to smooth out toppings. Using tip of knife, gently swirl toppings, forming marble design. Chill cake uncovered overnight.
*The original recipe calls for walnuts. I have have also made the crust with toasted pecans. Of the three, I prefer the almonds.
**I am fortunate to live in an area with a grocery store that besides lemon, they also have orange and lime curd. When I use the other flavors, I also change the concentrate to orange and/or lime depending on the curd flavor. All three citrus flavors make this a wonderful cheesecake.