Heat oven to 325, line an 8"-square baking pan w/ foil and spray w/ cooking spray. In bowl mix cracker crumbs, 2 tbsp sugar, 1 tsp grated lemon zest and melted butter until combined. Press mix into bottom of pan. Bake 10 mins, let cool.
In lg bowl, beat cream cheese, eggs, 2 tbsp lemon zest, lemon juice and 1/2 cup brown sugar until smooth. Pour cream cheese mix over crust.
In small bowl, mix remaining brown sugar, flour and cold butter, ( you may want to cut the butter up first, ) mix w/ fingers until crumbly. Sprinkle over cream cheese mix. Bake 35-40 min, or until center is almost set, it will jiggle lightly when moved. Refrigerate 1 hr to set. Cut into 9 bars.