To make the crust, place the wafers in a food processor fitted with the metal blade and process until finely crushed. Add a couple of drops of water. Press the mixture evenly and firmly onto the bottom of a springform pan (see note below), making a fist and using the back of your hand and fingers. Refrigerate the crust while you make the filling.

Preheat oven to 325 degrees.

Using an electric mixer with the paddle attachment, beat the cream cheese until smooth. On low speed, add the sour cream and vanilla and set aside. In a clean mixing bowl, using the whisk attachment, combine the eggs and 1 cup of the sugar. Whisk for 4 to 5 minutes until fluffy. Fold in the softened cream cheese mixture. Separate this mixture into two large glass bowls. To one of the bowls, add the raspberry puree, mix well.

In another bowl, using an electric mixer with clean, dry beaters, beat the egg whites. Start at low speed and increase the speed as the peaks form. Slowly add the remaining 1/2 cup sugar. When the whites are stiff but not dry, scrape them equally into the two bowls of filling and use a spatula to gently fold them in. Don't overmix the filling.

Pour alternating plain mixture and raspberry mixture into the prepared pan until the pan is filled. Bake for approximately 1 hour, until the cake has risen and browned slightly and it just shimmies when you gently move the pan. It's a good idea to place the springform on a low, flat, pan, such as a pizza pan, to catch any batter that leaks. Turn the heat off and let the cake stand in the oven for 1 hour more. Remove the cake from the oven and cool before serving. You can make this cake a day ahead.

process very fine in a food processor, and strain through a very fine sieve.

and halfway up the sides with foil to prevent any leaking batter from landing on the bottom of your oven and burning.