fresh tuna rosemary bay leaves olive oil onions thyme black peppercorns kosher salt lemons
3 cups good-quality olive oil (but not best); more if needed to cover the tuna during cooking
1 medium yellow onion, cut in 1/2-inch slices
2 sprigs fresh rosemary
6 sprigs fresh thyme
1 bay leaf
1 tsp. black peppercorns, coarsely cracked
Zest of 1 lemon, pared in strips
3 Tbs. coarse salt
2 lb. top-quality fresh tuna (yellowfin or ahi), cut into 1-inch-thick steaks