Preheat Oven and Prepare Baking Sheet: Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat.
Mix Dry Ingredients: In a large mixing bowl, whisk together the all-purpose flour, salt, garlic powder, and onion powder (if using).
Add Sourdough Discard and Butter: Stir in the sourdough discard and melted butter into the flour mixture. Mix until combined. It should start to resemble a dough.
Add Cheese: Fold in the finely grated sharp cheddar cheese until evenly distributed throughout the dough. If the mixture is too dry and crumbly, add water one tablespoon at a time, just enough to bring the dough together.
Roll Out the Dough: Dust a clean surface with flour. Turn the dough out onto the surface and roll it out to about 1/8 inch (3 mm) thickness. Aim for an even thickness to ensure uniform baking.
Cut Into Crackers: Use a pizza cutter or a sharp knife to cut the dough into squares or rectangles. Transfer the crackers to the prepared baking sheet. If you like, you can prick each cracker with a fork to prevent them from puffing up too much during baking.
Bake: Bake in the preheated oven for 15-20 minutes, or until the crackers are crispy and golden brown around the edges. The baking time may vary based on the thickness of your crackers and your oven, so keep an eye on them.
Cool: Let the crackers cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely. They will continue to crisp up as they cool.
Serve: Enjoy your sharp cheddar sourdough discard crackers as a snack on their own, or pair them with dips, soups, or salads.