Place flour, sea salt, baking powder and sugar in the bowl of a food processor and pulse to combine. Add the cubed butter, and pulse 3 - 5 times until the butter is the size of peas. Drizzle in water over the flour mixture and pulse another 3 - 5 times until the dough is just starting to come together. It will look very crumbly, but the dough should stick together if you pinch a little bit your fingers.
Dump the dough on to a clean work surface, and bring together using your hands. Press and squeeze the dough until it starts to hold together, then form into a flat disc. Don't overwork the dough here. You should still see bits of butter throughout the dough.
Wrap the dough tightly in plastic, and chill in the refrigerator for at least an hour (or up to 1 day).