When zesting lemons for the best possible flavor in your recipe, be sure to start with organic lemons and get the outermost part of the peel because it contains the most essential oils. The white part of the peel is to be avoided because it contains less oils and more bitter flavors. If you're zest is for decorative purposes it's ok to get the white part because thicker zest curls are more important for the overall look of the recipe.