Move oven rack to lowest position in oven and preheat oven to 350°. Grease a 3"-deep 8" round one-piece cake pan all the way up to the rim, including the rim itself, with butter. Mix lemon zest and juice in a small bowl.
Put cream cheese into the bowl of a standing mixer and beat on medium high, scraping sides and bottom of bowl with a rubber spatula often, until completely smooth. Beat in vanilla and sugar well. Add eggs one at a time, beating well after each addition, but do not beat any more than necessary to mix. Stir in lemon zest and juice with the spatula.
Generously spray the buttered cake pan with nonstick spray, then pour in batter. Place cake pan inside a larger 3"-deep pan. Place it in oven and pour hot water into larger pan, about 1 1⁄2" deep. Bake until top of cake is rich golden brown and feels dry to the touch, 1 1⁄4-1 1⁄2 hours (cake will be soft inside and become firm when cooled and refrigerated).
Lift cake pan out of water and place it on a cake rack. Let cake cool in pan for 3 hours. Cover pan with plastic wrap. Place a flat plate on top, invert, and remove pan. Sprinkle bottom of cake with cracker crumbs. Gently place another flat plate on top of crumbs. Very carefully invert again (without squashing cake), leave plastic wrap in place, and refrigerate cake overnight. Very carefully remove plastic wrap.