In a large saucepan, place the red potatoes.
Add vinegar, cooking salt, and enough water to just cover the potatoes.
Bring to a boil.
Boil, partially covered, for 15-20 minutes, adjusting the time depending on the size of the potatoes, or until the potatoes are tender.
Drain.
Preheat a 5- or 6-quart air fryer to 400°F for 3 minutes.
Transfer the boiled potatoes to a large oven tray.
Using a potato masher or the back of a spoon, gently press down on the potatoes until they are slightly flattened and the skins split.
Brush the potatoes with olive oil.
Carefully pull out the air fryer pan and basket.
Place the potatoes in the basket.
Slide the pan and basket back into the appliance.
Keep the temperature set at 400°F and set the timer for 30 minutes.
Turn the potatoes twice during the cooking time.
After 10 minutes, add the garlic, and in the last 5 minutes, add the rosemary.
Continue cooking until the potatoes turn golden.
To serve, generously season the smashed potatoes with salt.
Enjoy your salt and vinegar smashed potatoes!
