Butter or spray the bottom and sides of a 9-inch springform pan. Wrap the outside of the pan with 2 layers of heavy-duty aluminum foil to prevent leakage. The foil should come all the way up the sides of the pan because the cheesecake will bake in a water bath.

In a bowl, mix the crumbs and butter well. Pat the mixture firmly into place on the bottom of the prepared pan and refrigerate for 1 hour.

Preheat the oven to 350ºF.

In an electric mixer, beat the cream cheese until smooth. Add the sugar gradually and beat until completely blended. Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl once or twice. Add the lemon juice and lemon zest, then add the mascarpone and beat until smooth. Pour into the prepared pan.

Place the cake pan in a larger pan and add boiling water to come halfway up the sides of the cake pan. Bake for 1 hour, rotating the pan after 30 minutes for even cooking. It will be lightly colored on the top. Remove from the oven and let cool in the water bath. As it cools, it will shrink a little from the sides of the pan.

When completely cool, remove the pan sides and slide the cheesecake onto a plate. Cover and refrigerate. Serve chilled.