Brown butter tamarind sauce:
Combine tamarind, fish sauce, soy sauce, palm sugar, and vinegar. Set aside.
Pat steak dry with paper towels. Season steak with salt and pepper.
In a skillet over high heat, sear steak on all sides. Use weights if you have them. About 3-5 minutes each side.
Transfer steak to a plate and discard oil.
Lower heat to medium. Add butter to pan and brown by swirling the pan continuously until milk solids have turn a light brown. Keep a close eye as it can burn quickly. About 6 minutes.
Turn heat off and carefully add tamarind mixture. Swirl until combined. Turn pan back on to medium high heat. Add steak back to pan.
Baste steak with tamarind brown butter mixture until your desired internal temperature. For medium rare an instant read thermometer should read about 125F before rest. It will carry over cook to 130-135F.
Remove from pan and rest for at least 10 minutes before slicing.
Top with scallions and chiles and enjoy with some coconut rice.
