In a glass storage container or medium bowl, combine soy sauce, sesame oil, rice vinegar, brown sugar, ½ cup green onions, garlic, ginger, and sesame seeds.
Add steak to container and flip several times to coat.
Cover and refrigerate for 3-12 hours.
Preheat grill to 350°F.
Grill for 6-8 minutes per side or until internal temperature reaches 120°F. Cooking time will depend on the thickness of your steak and the temperature of your grill. Remove steak from grill and let rest 10 minutes before slicing.
While steak is cooking, pour remaining marinade into a small saucepan. Bring to a simmer and simmer until reduced and thickened slightly.
Slice steak into ½" slices. Serve over sticky rice, if desired. Drizzle with cooked sauce. Top with sliced green onions. Enjoy!
Notes
The ribeye cap is a super tender piece of meat that runs along the backstrap. It is often removed because it doesn't stay connected to the backstrap very well and it's an odd shape. But don't throw it in the grind pile! It's a delicious steak that might even be better than the backstrap!
You can use this marinade for just about any steak cut from any animal. Venison, antelope, moose, beef, etc. will all work great!
To speed up the marinade preparation, use jarred minced garlic and ginger in place of the fresh garlic and ginger.
This steak can be grilled on a pellet grill, gas grill, charcoal grill, or on an indoor grill pan.