Much milder than liver but full of vitamins, minerals, and nutrition. Throughout history, lamb hearts have long been one of the most valued cuts of meat from a lamb. They're high in Vitamin B12 and B3, plus contain plenty of Omega 3 fatty acids and even have Vitamin A and C.
See the below recipe for Grilled Lamb Heart with Avocado, Pickled Red Onions, and Cilantro.
Pickled Red Onions:
Medium red onion, cut into 1/8"-thick slices
1/2 cup lime juice
2 tsp. kosher salt
1 tsp. granulated sugar
Place the onions, lime juice, salt and sugar in a resealable bag. Squeeze as much air out of the bag as possible and seal the bag. Gently massage the bag to help dissolve the salt and sugar. Refrigerate at least 12 hours and up to 3 days.