Whisk flour and salt together in a medium bowl.
Using the back of a fork, cut the butter into the flour, mixing and smushing it until it is well incorporated into the flour.
Stir in the water and sourdough starter and mix with a spatula until a shaggy dough forms.
Use your hands to gently knead the dough in the bowl, if necessary, to get the mixture to form a rough ball.
Turn the dough out onto a floured surface and knead for another 1 to 2 minutes or until it is smooth and not sticking to the work surface.
Cut the dough into 12 pieces for taco- or enchilada-sized tortillas or 6 pieces for burrito-sized tortillas.
Shape each piece into a ball.
Cover with a very light kitchen towel or plastic wrap.
Let the dough rest 30 minutes and up to two hours (at room temperature or 24 hours in the fridge).
Roll out each ball to about 6 to 8 inches (taco size) or 10 to 12 inches (burrito size) in diameter.
Heat a 12 inch non-stick or cast-iron pan (do not add any oil) on medium-high.
Lay the tortilla in the pan and cook until it puffs and little brown spots on the underside appear.
Turn with tongs or your fingers and cook again till lightly brown.
Once the tortillas cool, store them in an airtight bag or container at room temperature for up to 5 days or freeze for up to 3 months.
