In a large mixing bowl, whisk together the flour, baking powder and salt.
Pour the oil over the dry ingredients and use a rubber spatula or your hands to stir until the texture is slightly crumbly and the oil is well mixed and evenly distributed into the flour.
In a separate small bowl, whisk the sourdough starter and water until smooth.
Pour the mixture over the dry ingredients and use a rubber spatula to mix the dough into a shaggy ball.
Wet your hands and knead the dough directly in the bowl several times until the dough appears smooth (about 1 minute of kneading). You can also knead the dough on a floured surface if you find that easier.
Pinch off golf ball sized pieces of dough and roll into balls. You should have enough dough for 8 tortillas.
Cover the dough balls with a slightly damp tea towel or plastic wrap and allow to rest at room temperature for 30 minutes.
Use a rolling pin to roll out the tortillas on a lightly floured surface until they are ¼ inch thick. You can roll them out as you cook them or prep them first and layer them with parchment paper between them to separate them.
Heat a large cast iron skillet over medium-high heat. Make sure the pan is hot before you start cooking the tortillas.
Place a single tortilla in the pan and cook on each side about 30 seconds. There should be golden brown spots on each side when ready. (The tortillas will puff up, but don't flatten them or you will release all the steam, which can affect the texture).
Remove tortilla from pan and place on a plate. Cover with a towel to keep the tortillas warm and soft until ready to serve.