Combine the graham cracker crumbs and the melted butter. Divide the crumb mixture between the two 10-inch or four 7-inch cake pans. Press evenly over the bottoms and if you choose, the sides of the pans, using your hands. Reserve.
Mix the cream cheese and granulated sugar together on low speed, using the paddle attachment until completely smooth. Mix in the cornstarch, lemon zest, and vanilla. Mix until smooth, scraping down the sides and the bottom of the bowl. Add the eggs and egg yolks a few at the4 time, blending thoroughly after each addition. Incorporate the sour cream.
Divide the batter evenly between the prepared pans.
Place the cake pans inside hotel pans or other suitable pans, adding hot water around the pans to reach about halfway up the sides. Bake at 350 degrees until set, approximately 50 min. (35 min for the smaller size). Cool completely then chill before moving the cakes from the pans. Decorate the tops of the cake with thinly slices fresh fruit, serve fruit on the plate next to a slice of cake, or serve the cheesecake with a thick fruit sauce such as blueberry sauce, strawberry sauce, etc.