Combine graham cracker crumbs and melted butter in a medium bowl.
Stir until the crumbs are evenly moistened.
Press the crumb mixture firmly into the bottom of a 9-inch pie plate or springform pan. Use the back of a spoon or measuring cup.
Chill the prepared crust in the refrigerator for at least 10 minutes while you prepare the filling.
In a large mixing bowl, beat the softened cream cheese with an electric mixer on medium speed until completely smooth and creamy.
Gradually add the sweetened condensed milk, mixing until fully incorporated.
Stir in fresh lemon juice, lemon zest, and vanilla extract until well combined.
Pour the filling over the chilled crust and smooth the top.
Chill the cheesecake in the refrigerator for at least 4 hours or overnight, until set.
Serve chilled, optionally garnished with a dollop of whipped cream and fresh lemon slices.