In a medium bowl, combine graham cracker crumbs, sugar, and melted butter. Press the mixture firmly into the bottom of a parchment-lined 9x9 inch baking pan. Chill while preparing the filling.

In a large mixing bowl, beat softened cream cheese until smooth. Add powdered sugar, vanilla extract, lemon zest, and lemon juice. Mix until fully incorporated.

In a separate bowl, beat the heavy cream until stiff peaks form. Gently fold the whipped cream into the lemon cheesecake mixture.

Spread the filling evenly over the prepared crust. Smooth the top and refrigerate for at least 4-6 hours, or overnight, until fully set.

Slice into bars and garnish with lemon slices and whipped cream before serving, if desired.