The white pith that sits right beneath the colorful skin is what makes citrus peel bitter. To get the flavor of citrus without the bitter pith, use a microplane to shave the colorful skin. Here's How to Zest A Lemon without the bitter pith. This skin contains the flavorful, fragrant oils of its fruit. On the other hand, orange marmalade takes that super bitter peel and turns it into a yummy bitter-sweet topping.