Total Time: 15 minPrep: 10 minCook: 5 minYield: 8Level: easy
Whisk curry paste, fish sauce, rice vinegar, coconut milk, black pepper, cayenne pepper, and salt together in a large shallow glass or ceramic bowl. Add the flap steak and turn to evenly coat. Cover the bowl with plastic wrap and marinate in the refrigerator for 4 to 12 hours.
Remove the flap meat from the marinade and shake off excess. Discard remaining marinade.
Preheat an outdoor grill for high heat and lightly oil the grate.
Cook flap steak on the preheated grill until it starts to firm and is reddish-pink and juicy in the center, 2 to 3 minutes per side. An instant-read thermometer inserted into the center should read 130 degrees F (54 degrees C). Transfer meat to a plate to rest for at least five minutes before slicing against the grain.
This recipe does not contain many non-starchy vegetables. To maximize your results, it is highly recommended that you eat at least three servings of non-starchy vegetables via a SANE side dish or green smoothie along with this main dish.