This is one of my favorite recipes.  We have this weekly.  It is so easy and nutritious.  Try it. 

2 Yellow fin Tuna steaks (great ones found in the freezer section of Trader Joe's)
Olive Oil
Sea Salt

Brush thawed tuna steaks w/olive oil and sprinkle with sea salt.  Grill on medium heat for 5-10 minutes depending on thickness.  Do not overcook (are best if a little pink in the middle)

Sauce:
1/4 c Whole fat plain yogurt
2 spoonfuls capers
1/4 red onion
1/2 squeezed lemon juice

Mix all ingredients in a bowl and put on top of tuna steak.  Serve on a whole wheat bun or eat skip the bun.  It is great either way.

Enjoy and let me know what you think.   My husband likes to prepare this one.  The recipe can be found on this website:  www.samthecookingguy.com.
(measurements might be different, I just guesstimate).