Step 1

For lemon curd, grate lemons for 1-1/2 teaspoons zest. Squeeze lemons for 1/2 cup juice; strain juice. In a medium heavy saucepan, whisk together 2 eggs, 2/3 cup sugar, 1-1/2 teaspoons lemon zest and 1/2 cup lemon juice. Add 6 tablespoons cubed butter. Cook over medium heat, whisking constantly, until lemon mixture thickens and bubbles all over. Strain mixture over a sieve, pushing it through with a spatula as needed. Cool.

Step 2

Preheat oven to 375 degrees. For crust, in a large bowl, stir together crushed graham crackers and 1/2 cup melted butter until crackers are moistened. Press mixture onto bottom and about 1 inch up the sides of a 9-inch spring form pan. Bake for 5 minutes or until edges are light brown. Cool on a wire rack. When cool, place crust-lined pan on a double layer of 18-by-12-inch heavy-duty foil. Bring edges of foil up and mold around sides of pan to form a watertight seal.

Step 3

Reduce heat to 325 degrees. For filling, in a mixing bowl, beat cream cheese with an electric mixer on medium speed for 3 minutes or until smooth. Gradually add remaining 1 cup sugar, beating until well blended. Add remaining 4 eggs, one at a time, beating on low just until combined. Beat in vanilla.

Step 4

Pour two-thirds of cheesecake mixture (about 4 cups) into crust-lined pan. Carefully spoon 1 cup lemon curd over top. Using a table knife, gently swirl cheesecake mixture and curd. Spoon remaining cheesecake mixture over top. Gently swirl remaining curd into cheesecake mixture.

Step 5

Place spring form pan in a large roasting pan. Pour enough boiling water into roasting pan to reach halfway up sides of spring form pan. Bake for 1 hour or until cake edges jiggle slightly when spring form pan is gently shaken. Turn oven off and leave cheesecake in oven, with door shut, for 60 minutes.

Step 6

Carefully remove spring form pan from water bath. Remove foil from pan. Cool cheesecake in spring form pan on a wire rack for 15 minutes. Using a small sharp knife, loosen the crust from sides of pan; cool for 30 minutes. Remove sides of pan; cool cheesecake completely on rack, about 1 hour. Cover and chill at least 4 hours before serving.