Make crust: Preheat oven to 325 degrees F.
Lightly spray a (9-inch) springform pan with cooking spray. Mix crumbs and 1/4 cup unsalted melted butter in a bowl. Press crumb mixture onto bottom and 1 1/2 inches up side of pan. Bake for 8 to 10 minutes or until edges are lightly golden and crust is set. Cool on rack.
Make filling: In large bowl with electric mixer on medium-high, beat cream cheese and sour cream for 2 to 3 minutes until fluffy. Gradually beat in 2 cups sugar or sugar substitute. Beat in 3 eggs, 1 at a time, just until incorporated. Beat in 2 teaspoons lemon zest and 2 tablespoons lemon juice.
Pour into crust. Bake for 1 hour to 1 hour, 15 minutes, or until center is almost set, but still slightly jiggly. (Do not overbake, as it will firm as it cools). Let cool completely.
Make lemon curd: In the top of a double boiler, combine 1 1/2 teaspoons lemon zest, 6 tablespoons lemon juice, 1 large egg, egg yolk, and 1/2 cup sugar or sugar substitute over gently simmering water. Whisk until hot and frothy, about 5 minutes. Gradually whisk in 2 tablespoons unsalted butter and continue whisking for 7 minutes or until thickened and coats back of spoon. Remove from heat and cool for 30 minutes.
Run a thin blade around the edge of the springform pan and remove sides. Transfer to a serving plate. Spread lemon curd over top. Let stand at room temperature for 30 minutes. Garnish with raspberries and zest, if desired. Cool cheesecake in refrigerator several hours or overnight before serving.