Preheat oven to 300° F. Break cookies and place in food processor.* Pulse until ground into medium-fine crumbs. Put into medium mixing bowl, and stir in butter and sugar. Turn out into a buttered nine-inch springform pan and, using your fingers, press mixture into an even crust along the bottom. You can also use a buttered glass pie plate and form the crumbs into a traditional crust along the bottom and up the sides. Bake for 10-15 minutes until firm and dry. Remove from oven and set on a wire rack.
*Don't have a food processor? You can also make crumbs in the blender or by hand. Place crackers in a heavy duty plastic freezer bag and crush with a rolling pin.
If you used a food processor to make the crust, just wipe it out with a dry paper towel and clean off the blade. Pulse eggs a few times to beat (or use an electric mixer). Pulse in sugar, cornstarch, salt, vanilla, and yogurt until light and slightly bubbly. Add lemon and lemon zest and pulse or beat briefly to incorporate. Pour mixture into prepared crust (it's fine if the crust is still warm).
Place in center of oven. Start checking cheesecake after 50 minutes and then every 5-10 minutes after that. Shake pan gently. The filling should look creamy but firm at the edges, and still appear slightly jiggly in the center. It will firm up as it cools. Remove from oven and set on a wire rack. Cool to room temperature. Refrigerate for at least 4 hours (or overnight) before serving.
Optional topping: 3 cups sliced strawberries, raspberries, blackberries or mixed berries tossed with two tablespoons sugar. Let mixture sit in the refrigerator for at least an hour so the berries get nice and juicy. Spoon desired amount of topping over a slice of cheesecake before serving.