Preheat oven to 350-degrees. Line an 8x8 or 9x9 inch baking dish with aluminum foil and apply non-stick cooking spray.
Cream together butter and both sugars. Add lemon juice, eggs, and vanilla extract, and beat until combined.
In a separate bowl, stir together the dry ingredients: flour, lemon zest, baking powder, and salt. Gradually add the flour mix into the wet ingredients.
Stir in white chocolate chips; dough will be thick. Spread into the bottom of the ready baking dish. An offset spatula works well to smooth it out. If desired, sprinkle sparkling or turbinado sugar all over the top.
Bake for 20-25 minutes, until it passes the toothpick test.
Set on a wire rack to cool completely, then use foil to lift contents to a cutting board. Cut into bars.
OM NOM NOM!