Wash potatoes thoroughly and pierce each with the tip of a knife. Wrap in a damp paper towel and cook in 3 minutes intervals in the microwave until tender, but firm.
Heat a large cast-iron skillet over medium heat. Add 1/3 cup oil. I usually use avocado oil, but you can also use canola. Cut the potatoes to your desired size.
Add chopped onions after the first flip of the potatoes & wait another 3 mins before touching the pan. Then turn potatoes and onions occasionally until crispy. About 5 more minutes.
Sprinkle the potatoes and onions with salt and pepper. Transfer the potatoes and onions to a baking sheet lined with paper towels to remove excess oil.