Rinse and drain the Lumpfish caviar. Line bottom of 10-inch springform pan with waxed paper.
Mix bread crumbs, 1/2 cup melted butter and parmesan cheese in small bowl. Press crumb mixture firmly against bottom and sides of springform pan. Refrigerate pan while preparing the filling.
Mix cream cheese, eggs, onion and lemon extract in a food processor or blender until smooth. Blend in 1/4 cup melted butter. Transfer to bowl. Stir in sour cream. Gently fold in the caviar. Spoon filling into chilled crust.
Bake at 350°F for 45 minutes. Turn off oven. Let cheesecake stand in oven 15 to 20 minutes; filling will appear unset.
Remove from oven; cool to room temperature. Cover with plastic wrap and refrigerate at least 12 hours before serving.