Make lemon curd whisk together zest, juice, sugar, and eggs in a 2-quart heavy saucepan. Add butter and cook over moderately low heat, whisking frequently, until curd is thick enough to hold marks of whisk and first bubbles appear on surface, about 6 minutes. Force lemon curd through a fine-mesh sieve into a wide shallow dish, scraping bottom of sieve then cover surface with wax paper. Cool completely, stirring occasionally, about 30 minutes. Cooks' Notes: Lemon curd can be made 1 week ahead and chilled, covered.
Make and bake crust. Crust (without filling) can be made 1 day ahead and kept, covered, at room temperature.
Put oven rack in middle position and preheat oven to 350°F Invert bottom of spring form pan (to make it easier to slide cake off bottom), then lock on side.
Stir together crust ingredients in a bowl, then press onto bottom and 1 inch up side of spring form pan. Place spring form pan in a shallow baking pan and bake 10 minutes, then cool crust completely in spring form pan on a rack.
Make filling and Bake Cheesecake:.
Reduce oven temperature to 300°F Beat together cream cheese and sugar in a bowl with an electric mixer at medium speed until smooth, 1 to 2 minutes. Reduce speed to low and add eggs 1 at a time, beating until incorporated. Beat in sour cream and vanilla until combined. Pour two thirds of cream cheese filling into crust, then spoon half of lemon curd over filling and swirl curd into filling with a small knife. (Avoid touching crust with knife to prevent crumbs getting into filling.) Repeat with remaining filling and curd. Bake cheesecake until set 1 1/2 inches from edge but center trembles when pan is gently shaken, about 45 minutes. (Center of cake will appear very loose but will continue to set as it cools.).
Transfer spring form pan to a rack and immediately run a knife around top edge of cake to loosen. Cool completely, about 2 hours, then chill. Uncovered, at least 4 hours. Remove side of spring form pan before serving. Cheesecake can be chilled, loosely covered, up to 2 days. Cheesecake must be completely chilled before covering to prevent condensation on its surface.
Combine blueberries, sugar and lemon juice in a medium saucepan. Over low heat, cook mixture, mashing blueberries slightly, until sauce has reduced and slightly thickens, about 5 minutes. Remove from heat and let cool slightly. Serve warm over cooled cake.
Special equipment: a 9- to 91/2-inch (24-cm) spring form pan.
Note:I will use a 8" or 6" spring form pan for a small cheesecake when we are feeling peckish and slice the cheesecake in desired thickness wrap in cling wrap of your choice and then wrap in foil freeze up to 8 weeks for maximum quality.
