This is similar to the Fresh Tuna Salad with Simple Lemon Dijon found in the South Beach Diet Quick and Easy Cookbook, but I’ve substituted snow peas for the green peas.
2 T lemon juice
1 T minced red or sweet onion
1 t Dijon mustard
1/4 C plus 2 t canola oil
1 lb fresh tuna, about an inch thick
1 head Bibb or Boston lettuce, torn into bite-sized pieces (you can also use leaf lettuce or Romaine)
1 C snow peas
Salt and pepper
Garnish: 2-4 T finely minced red bell pepper
The dressing: Whisk together the lemon juice, onion, and mustard. Slowly whisk in 1/4 C of the oil. Season with salt and pepper. (You can also do this in a blender)
The tuna: Season the tuna with salt and pepper. Heat 2 t oil in a large skillet over medium-high heat. Cook the tuna for 1-1/2 minutes per side for medium-rare, or longer if you prefer. Transfer to a cutting board and slice.
The peas: Bring a couple of cups of water to a boil in a small saucepan. Drop in the snow peas and cook for a minute, then drain, cool under cold running water, and drain again.
The assembly: Divide the lettuce among serving plates and sprinkle with the snow peas. Put the tuna on the top and drizzle with the dressing. Garnish with finely minced red bell pepper.