Place the evaporated milk in the refrigerator several hours before starting the recipe. For best results, chill your mixing bowl and beaters as well.
Add the lemon gelatin to a medium bowl. Pour in the boiling water and stir until the gelatin is completely dissolved. Let it cool until slightly thickened but still pourable.
Add 2½ cups of graham cracker crumbs to a medium bowl. Stir in the melted butter and 2 tablespoons of sugar until evenly combined.
Press the crumb mixture firmly into the bottom of a 9×13-inch baking dish. Reserve the remaining ½ cup of graham cracker crumbs for the topping.
In a large bowl, beat the softened cream cheese until smooth.
Add 1 cup of sugar, lemon juice, and vanilla extract. Beat until creamy and well combined.
Slowly mix the cooled lemon gelatin into the cream cheese mixture on low speed. Scrape down the sides of the bowl.
In a chilled bowl, beat the cold evaporated milk on high speed until fluffy and increased in volume.
Gently fold the cream cheese mixture into the whipped evaporated milk until fully combined.
Spoon the filling over the prepared crust and spread into an even layer.
Sprinkle the reserved graham cracker crumbs over the top.
Cover and refrigerate for at least 6 hours or overnight.
Slice into squares and serve cold.