Preheat the oven to 350 degrees F. Position a rack in the center of the oven. Spray a 9 x13 x 2-inch baking pan with nonstick cooking spray.
For the crust, combine the graham cracker crumbs, sugar, and butter in a medium bowl and mix until moistened. Press the mixture evenly in the prepared pan and 1/4 inch up the sides. Bake for 8 minutes and set aside to cool.
For the filling, place the cream cheese and sugar in the bowl of an electric mixer fitted with the paddle attachment. Beat on medium speed for 3 minutes, until light and fluffy. Add the ricotta and beat for another minute, scraping down the bowl. With the mixer on low, add the limoncello, vanilla, and lemon zest and beat for one minute. With the mixer on medium-low, add the eggs, one at a time, until incorporated. Scrape down the bowl and mix until the batter is smooth. Pour over the crust.
Place the baking pan in a roasting pan large enough to hold the baking pan completely flat. Place the pan in the oven and carefully pour enough of the hottest tap water into the roasting pan to come halfway up the sides of the baking pan. Bake for 50 to 55 minutes, until almost set in the center. (It will still be a little jiggly when you shake the pan gently.) Turn off the heat and leave the cheesecake in the oven in the water bath for 15 minutes to prevent the cheesecake from cracking. Take the baking pan out of the water bath and place on a rack to cool completely. Wrap the entire pan with plastic wrap and refrigerate for at least 6 hours or overnight. Sprinkle with extra grated lemon zest, cut in 12 pieces, and serve cold.