Preparation

• 将柠檬汁和刺山柑在1 QT中。耐热测量杯。将黄油和奶油带入快速煨的小型热量，经常搅拌。混合物起初将看起来均匀，然后将分开并开始变成金黄色。继续搅拌，直到它变成黑色锈色，总计约10分钟。小心地将棕黄油混合物倒入柠檬汁中;黄油会沸腾和溅射。搅拌结合并返回平底锅，从热量上脱离。
• Sprinkle the tuna on both sides with the fennel seeds, salt, and pepper. Heat the oil in a 10- to 12-inch heavy skillet (preferably cast iron) over medium-high heat until shimmering hot. Sear the tuna on both sides until done to your liking, about 2 minutes per side for medium rare (still raw in the middle) or 3 minutes per side for medium (just pink in the middle). Transfer the tuna to plates. If necessary, quickly reheat the sauce. Serve the tuna drizzled with the sauce.

This tuna is delicious sprinkled with fresh parsley, and it pairs well with roasted fennel.