Line an 9 inch pan with foil and lightly spray with cooking spray. Set aside. In a food processor combine graham cracker squares and pulse until crumbs are formed. Add melted butter, and brown sugar. Press into the bottom of your 8 inch pan. Chill while you make the filling.
To make the filling: In a large bowl, combine cream cheese, condensed milk and beat on high with an electric mixer until smooth and creamy, about 2 minutes. Add lemon zest and juice and beat until fully incorporated, another 30 seconds.
In a small bowl, combine the gelatin and boiling water and whisk until gelatin is entirely dissolved; let cool 2 to 3 minutes. Stir the gelatin into the cream cheese-lemon mixture until well incorporated. Pour the filling over the crust. Refrigerate for 8 hours or overnight, until filling is firm.