Step 1

Combine orange pieces, lemon juice, lemon zest, orange juice, rice vinegar, soy sauce, maple syrup, honey, garlic cloves, ginger, pepper, and cayenne pepper in a blender; blend until marinade is smooth. Mix in green onions.

Step 2

Place flank steak into a shallow baking dish and pour marinade over meat, making sure marinade gets underneath the meat as well. Cover the dish, refrigerate, and marinate for at least 2 hours, or overnight.

Step 3

Remove steak from the refrigerator and allow to come to room temperature for at least 30 minutes before grilling. Lift up steak from the dish to let juices run off; reserve marinade.

Step 4

Preheat an outdoor grill for medium-high heat and lightly oil the grate.

Step 5

Cook flank steak on the preheated grill until it begins to firm and is reddish-pink and juicy in the center, 5 to 7 minutes per side. An instant-read thermometer inserted into the center should read 130 degrees F (54 degrees C).

Step 6

Cover steak and set aside to rest for 10 minutes before slicing thinly against the grain.

Step 7

While steak is resting, pour remaining marinade in a saucepan over medium-high heat and bring to a boil. Cook until sauce is reduced, about 5 minutes. Serve with the flank steak.