In a large mixing bowl, whisk together the flour and salt. Using your fingertips, cut the softened butter into the flour until the mixture resembles coarse sand. It should stick together slightly when pressed between your fingers.
1 ¾ cups (210 grams) all-purpose flour, 3 tablespoons (42 grams) unsalted butter, 2 ½ teaspoons (7 grams) kosher salt
Add the sourdough discard and water to the mixing bowl. Mix and knead lightly until a soft, slightly sticky dough forms.
7 tablespoons (100 grams) water, ½ cup (113 grams) sourdough starter discard
Divide the dough into 6 or 12 equal-sized pieces. Roll each piece into a ball, cover lightly, and allow them to rest at room temperature for about 20 minutes or up to 2 hours. Alternatively, ferment them in the refrigerator for up to 2 days.
On a lightly floured work surface, roll each ball out into a round tortilla, making sure to roll them out as thinly as possible (you should be able to just see the counter through the tortilla). I recommend rolling out most or all of the tortillas before you start cooking them. Tortillas cook very quickly so it's best to have them ready to go.
Preheat a cast iron skillet or stainless steel skillet over medium heat. Do not add any oil to the skillet. Once the skillet is very hot, add your first tortilla. Cook for about 30 seconds or until bubbles begin to form on the surface of the tortilla. Flip and cook for an additional 30 seconds on the other side.
Note: The first few tortillas are usually paler and don't puff up quite as nicely. This happens when the skillet isn't quite up to the right temperature yet. Cook a few and adjust the temperature of your burner accordingly.
Repeat with the remaining tortillas. Place the cooked tortillas on a plate and cover them lightly with a clean tea towel to keep them warm and moist. Serve with your favorite taco, burrito, or quesadilla fillings and enjoy!