In a mixing bowl, combine flour and sugar for the crust. Stir in melted butter until well combined. Press mixture into the bottom of a greased baking dish.
Bake crust for 15 minutes or until lightly golden. Remove from oven and set aside.
In another bowl, whisk together sugar and flour for the filling. Add eggs, lime juice, and lime zest, and whisk until smooth.
Pour filling over the baked crust. Bake for an additional 20-25 minutes or until the filling is set.
Let cool completely before cutting into bars. Dust with powdered sugar if desired.