First, make the crust dough. Combine the flour, baking powder, seasoned salt, and dried tarragon in the bowl of a food processor. Pulse it a couple of times to aerate those dry ingredients. Then add in the butter and pulse it some more until it resembles pebbly sand. Finally, add in the ice water and pulse it until it comes together into a gorgeous dough. Take the dough and form it into ball. Place it on a big sheet of plastic wrap and press it into a small disc. Wrap the disc in the plastic wrap and chill it for 30 minutes in the refrigerator.