Preheat a grill or grill pan on medium heat.
Prepare rice noodles according to directions listed on package.
In a mixing bowl, whisk together brown sugar, soy sauce, beef broth, rice vinegar, lime juice, set aside.
Season the steak generously on both sides with salt and pepper. Grill the steak to your desired temperature using a thermometer. (see below) Then set on a cutting board for 3 minutes to rest.
Heat the oil in a nonstick pan on medium heat. Add the bell pepper and carrots saute 5 - 6 minutes; then add the bok choy, garlic; saute for 2 - 3 minutes. Add in the soy sauce mixture; cook until the bok choy become tender, about 4 - 5 minutes.
Toss in the noodles. Slice the steak against the grain and serve over the noodles and vegetables. Garnish with peanuts and cilantro.