Preheat oven to 180ºC / 350ºF / Gas Mark 4. Mix graham crumbs, 1/2 tablespoon sugar, and melted butter until blended; press onto bottom of 23cm (9") springform pan.
Beat cream cheese and 1 1/2 cup sugar in large bowl with mixer until blended. Add eggs, one at a time while mixing well on low speed. Add Ricotta cheese, lemon zest, flour and vanilla extract and mix thoroughly until mixture has a smooth and creamy texture. Pour mixture into crust. Bake 55 minutes to 1 hour and 5 minutes or until center is almost set.
Cool the cheesecake at room temperature completely. This may take up to 2 to 3 hours depending on the temperature of your home. Run a clean knife around rim of pan to loosen cake from the springform pan. Refrigerate cheesecake for at least 4 hours or overnight.
To make the topping, add jam to a saucepan on low heat. Simmer for 2-3 minutes. Remove from heat and stir in peaches. Refrigerate until ready to serve. Arrange topping on over cheesecake just before serving.