Fit paddle attachment to mixer.
Put flour, salt, and baking powder in mixer's bowl.
Using slowest speed, mix until ingredients are combined.
Cut frozen butter into small pieces, approx. ⅓" cubed.
Add butter to flour mixture.
Using slowest speed, mix until butter is thoroughly coated but not yet fully mixed into flour.
Add cider vinegar and water.
Using slowest speed, mix until ingredients start to clump together.
Remove dough from mixer.
Quickly squeeze dough together into a ball and shape into a log.
Divide dough into two parts, one slightly larger for the lower crust and the other slightly smaller for the upper crust.
Wrap two parts in plastic wrap.
Refrigerate wrapped dough until ready to use.