Prepare the Crust: Combine the graham cracker crumbs, brown sugar, salt, and melted butter in a bowl. Mix well until all crumbs are evenly moistened. Press the mixture firmly into the bottom and up the sides of a 9-inch pie pan, creating an even layer. Place in refrigerator to chill and set while preparing the filling.
Mix the Pudding Base: In a large bowl, whisk together the evaporated milk and instant lemon pudding mix on low speed for 2 minutes or until the mixture thickens. This creates the stabilizing base for your pie filling that will help it set properly.
Prepare the Cream Cheese Mixture: In another large bowl, beat the softened cream cheese with an electric mixer until light and fluffy, about 3 minutes. Proper beating at this stage ensures a smooth, creamy texture without lumps. Add the thawed lemonade concentrate and beat until well blended and smooth.
Combine the Fillings: Add the pudding mixture to the cream cheese mixture and beat until fully incorporated and smooth. Make sure to scrape down the sides of the bowl to ensure everything is evenly mixed.
Assemble the Pie: Pour the finished filling into the chilled graham cracker crust, spreading evenly with a spatula. Cover the pie with plastic wrap, being careful not to let the wrap touch the surface of the filling.
Chill and Serve: Refrigerate the pie for at least 4 hours or until completely set. For best results, chill overnight. Before serving, garnish as desired with whipped cream, lemon slices, or zest.