Steam the beef heart and marinate in soy sauce, finely chopped ginger, onion, lemon zest, ajinomato, sugar, chili pepper, sesame oil and garlic for 10 minutes.
Prepare XO sauce separately. Finely chop and mix garlic, onion, finely chopped ginger, fish sauce and vegetable oil.
To serve, cut the beef heart into slices, put on a plate, pour XO sauce. Decorate with cilantro and cashew nuts.