Rosy-Red and Raw

• High-end restaurants typically quickly sear tuna steaks to serve them with a brown char on the outside, a 1/4-inch border of light tan around each slice and a translucent center as rosy-red as raw meat. The reddish-pink interior is the same color as raw tuna and has a succulent texture. Restaurants are confident in serving rare tuna safely because they buy the freshest fish they can from reliable sources. The temperature of rare tuna is about 110 degrees Fahrenheit on a meat thermometer.

Medium-Rare Steaks

• Tuna steaks that are cooked to medium have the dark brown exterior and the same pale tan outer edges as rare tuna, but the tan extends almost to the center of each slice. The interior of medium-rare tuna resembles perfectly cooked pork in color, mostly whitish or tan with a pale pink and opaque look to it -- it's not shiny like rare tuna meat. Medium-rare 1-inch-thick steaks cook for about 3 minutes per side.

What the Government Says

• If you want to put safety before style, cook tuna steaks more thoroughly, until the center is opaque and uniformly light tan. Its temperature on a meat thermometer should register 145 F, according to the U.S. Department of Agriculture. To keep your steaks tender and avoid overcooking, cook them for the same amount of time as rare steaks, about 1 1/2 minutes per side, and then tent them with foil and let them rest until they reach 145 F from residual, carryover heat.

Tuna, Mercury and Polychlorinated Biphenyl

• Most large fish, such as some tuna, shark and swordfish, have unacceptable levels of mercury that are harmful to everyone and especially to children and pregnant women. Older tuna, such as fresh bluefin or ahi, also called yellowfin or bigeye, have more mercury than other types. Look for troll- or pole-caught tuna for fish with the least amount of mercury. If you eat bluefin tuna, don't eat the skin, and trim away excess fat to limit your exposure to PCB chemicals.