Wash & cut potatoes in half the long way. Then cut into wedges about 1/2 inch thick.
Add potatoes to pan with vinegar and water. Bring up to a boil and cook until just tender. Check with a fork (about 10 min).
Preheat oven to 400F.
While potatoes are cooking mix seasonings, flour, cornstarch & baking powder into a medium bowl.
Strain cooked potatoes & put back in pan or a large bowl. Add buttermilk and gently toss to soak for 5 min.
Add vegetable oil to a rimmed baking pan and put in oven to get hot.
Drain potatoes & then dredge them in powder mixture to coat evenly.
Put the potatoes in a fine strainer to shake off the extra powder. You don't want any areas to be too thickly clumped on or you may have some powdery bites.
Place potatoes on baking pan. The hot oil will help them get a fried texture.
Bake for 10 minutes then flip and bake until crust is golden brown (about 10-15 more minutes).
Remove from oven & salt potatoes. Optionally you can add other spices like rosemary & oregano. Or try seasoned salt for extra flavor.