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, starting with 4 tbsps water.
Using slowest speed, mix until ingredients start to clump together. Add more water if necessary.
Remove dough from mixer.
Quickly squeeze dough together into a ball and shape into a disc.
Wrap dough in plastic wrap.
Refrigerate wrapped dough until ready to use.