Preheat the oven to 350 degrees. Line a 9″ square baking dish with a piece of foil and spray it well with non-stick spray.
MAKE THE CRUST:
Combine the whole-wheat flour, all-purpose flour, powdered sugar, fresh rosemary, and salt.
Use a pastry cutter or a fork to cut the butter into the flour until the mixture resembles small crumbs.
Press the dough firmly and evenly into the bottom of the foil-lined pan.
Bake at 350 degrees until the crust is lightly browned, about 20 minutes.
PREPARE THE FILLING:
While the crust is baking, combine the lemon juice, granulated sugar, lemon zest, all-purpose flour, chopped fresh rosemary, baking powder and eggs. Whisk together until the mixture is smooth.
Pour the filling onto the hot crust and return the pan to the oven for another 20 minutes or until the filling is set. Remove from the oven to cool.
SERVE:
When the bars have cooled, remove them from the pan and carefully peel away the foil from the sides of the bars. Sprinkle with additional powdered sugar, cut into squares and serve.