Preheat oven to 325 degrees F.

In the bowl of an electric mixer with the paddle attachment cream together the butter, sugar, agave nectar and lemon zest. Scrape sides of bowl as necessary.

Turn off mixer and add flour and salt.

In a small bowl stir together the lemon juice and baking soda. Get ready for the fizz. Remember chemistry class? acid + base = fizz or kaboom or something

Add the lemon juice/baking soda mixture to the rest of the ingredients. Mix on low just until blended. Use a spatula to scrape down sides and bottom of mixing bowl and mix dough by hand to ensure that all ingredients are well incorporated.

Shape into 1-inch balls and place on parchment lined baking sheets. Place cookie sheet on baking rack in middle of oven. Bake for 10-15 minutes, just until cookies are very slightly brown on the edges. It is better to under-cook them slightly than to over-cook them. In my oven, the cookies only needed 11 minutes.

Remove cookies from oven and allow to cool for a few minutes on baking baking pan. Toss lightly in powdered sugar and place on cooling rack to finish the cooling process.