Preheat grill or grill pan and allow to get very hot.
Transfer steak to cutting board and allow to stand for 5 minutes. Cut across grain into thin strips.
Heat 1 tablespoon olive oil in a large cast iron frying pan or skillet on high heat. Place the steak in a hot pan and allow to sear for 3 to 4 minutes on each side, or until desired doneness. Transfer steak to cutting board and allow to stand for 5 minutes. Cut across grain into thin strips.
Quickly wipe down the pan and return to medium-high heat. Add remaining 1 tablespoon olive oil in the skillet. Sauté the peppers, stirring often, for about 6-7 minutes, or until softened and slightly caramelized.
*you can also use Thai sweet chili sauce & reduce honey to 1 teaspoon or use more) or add an additional 1 tablespoon of soy sauce instead if you can't find fish sauce or would rather not use it. It won't have that same umami flavor but will still taste great.
**To make ahead, you can prep the bell peppers in advance by cutting them into strips the night before and whisking the sauce together and storing it in a resealable glass containing while using the other half to marinate the steak overnight.