Combine the flour, baking powder, oil and salt and rub together until crumbly. Add the water and mix until the dough begins to come away from the edges of the bowl.
Remove from the bowl and knead for about a minute, dusting with a little flour as necessary to get an end product that does not stick to the bench, but is still soft and pliable.
Divide into four parts and then divide each of these in turn into four parts. Roll each of these into a small ball, place on a dish, cover with plastic, and place in the fridge for about half an hour to mature.
I use a cast iron frying pan to cook them in. A barbecue blacktop is fine also, but it takes a little experience to get the gas levels right. (You can do this with lightweight pans, but in my opinion there is too great a drop in temperature when a cold tortilla hits the metal.) Place a teaspoon of oil in the pan and wipe it around with a paper towel which you will keep handy. (I have been using rice bran oil lately for this sort of job - very fluid, and handles hottish temperatures well.)
Put the pan on the element at about 4/12 while you roll out the tortillas. The idea is to heat the entire pan evenly, so you don't end up with the first few tortillas burned in the middle and raw near the edges.
Roll the tortillas out as thinly as possible so they are about 200mm across and stack them by the pan ready to go. They may contract a little, so be prepared to give each one a quick re-roll as you are cooking the previous one.
Bring the temperature up to around 6.5/12, add a little more oil and wipe around again with the paper towel. Start cooking your first tortilla. You will notice small bubbles beginning to appear on the surface, and when that happens use tongs or a fish slice to flip the tortilla and begin the other side. (The cooked side should have a sprinkle of golden to light brown spots over its surface. Black, and the element is a little high.) You will notice the tortilla beginning to rise a little. Press down lightly on the top with a fish slice, give it a few more seconds, and then remove to a plate.
Add a half teaspoon of oil to the pan and wipe with the paper towel, or there may be sufficient oil on the towel already to do without the extra half teaspoon.
Repeat for the second tortilla. You can now grab number three and give it a quick roll out, and you should be finished by the time the second requires flipping. And so on.
Healthy, physically active teenagers can get through up to half a dozen of these, along with beans and sour cream.