Prepare a 9"x9" baking pan by lining it with parchment paper (along the bottom and up two sides). Grease the unlined sides with butter.
Prepare the crust by beating the butter (with an electic mixer) until smooth. Add flour and powdered sugar (slowly) and cream together just until well combined. Press mixture into the prepared pan. It may be helpful to occasionally wet your fingers with a bit of water so the mixture doesn't stick to them.
Bake crust at 325*F. for 12-15 minutes.
Prepare the filling by mixing all of the dry filling ingredients (coconut, brown sugar, walnuts, flour, baking powder, salt) together in a medium bowl.
In a small bowl, beat the eggs with a fork, the pour eggs into the bowl of dry ingredients. Add vanilla and still all ingredients until combined (can easily be done by hand).
Spread filling onto the pre-baked crust, and bake an additional 20-25 minutes.
Once the bars have baked, prepare lemon glaze.
In a medium bowl combine the powdered sugar, melted butter, lemon juice and zest. Stir with a whisk until smooth and well combined. Pour glaze on top of baked bars. Allow to cool at least 30 minutes.
If you are not a fan of nuts, feel free to omit the walnuts and increase the coconut. I have not made the recipe this way, so you may need to watch the baking time a bit more closely.