National Sourdough Bread Day 2021: How To Bake The Bread In 3 Easy Steps 04/01/21 AT 8:21 AM National Sourdough Bread Day is celebrated annually on April 1 to commemorate one of the oldest leavened bread in the world. What Is Sourdough Bread? Sourdough bread is made from a dough that is produced through a long fermentation process using lactobacilli and yeasts. Naturally occurring yeasts and friendly bacteria are used to cultivate it, which gives the bread a slightly sour yet pleasant taste. The bread can be consumed in a variety of ways and acts as a great side dish for any meal. Sourdough bread crumbs can also serve as flavorful toppings for soups and stews. It can also be eaten as toast for breakfast, among other ways.