Marinated Beef Tips

Make the marinade by combining 1 tablespoon neutral oil with the soy sauce, white wine vinegar and arrowroot or corn starch.
Toss half of the marinade in a medium bowl with the sirloin steak cubes. Let sit for at least 15 minutes, up to 30 minutes if you have the time.
While the beef is marinating, place the cubed potatoes in a bowl and sprinkle with 1-2 tsps of salt. Microwave for 3-4 minutes and then gently stir, and cook for another 3-4 minutes, just to parcook them. Make sure not to over stir or you will release too much of the starches and your potatoes will get sticky.
Once your beef is done marinating, heat 1-2 tablespoon of oil on medium high heat and sauté till partially cooked. Beef cubes should be browned on the outside but still rare internally. Remove beef and drippings from the pan and set aside.
Add 1 more tablespoon of oil to the pan, then add the cubed potatoes. Occasionally stir and cook for about 10 minutes, till just about fork tender.
Add in the onions and bell pepper, cooking for about 5 minutes just till tender, then add back in the beef and juices. Add in the remaining marinade and stir all together till well mixed. Let cook on medium low just till juices are all combined and beef has reached the desired doneness.
Tastes great served with lime wedges and sriracha hot sauce.