Low-Fat Cheesecake

INGREDIENTS

• Cooking spray
• 2 tablespoons unsalted butter, melted
• Assorted toppings
• 1 1/2 cups sugar
• 1 cup reduced-fat sour cream
• 2 tablespoons all-purpose flour
• 2 8-ounce packages Neufchatel cream cheese, softened
• 9 whole low-fat cinnamon graham crackers, broken in half
• 2 8-ounce packages fat-free cream cheese, softened
• 2 large eggs plus 3 egg whites
• 1 teaspoon finely grated lemon zest
• 1 teaspoon vanilla extract