Heat a pan on medium high heat and add some oil & lots of butter. Saute lots of spinach for 3-4 minutes while stirring and seasoning to taste with salt and pepper. Take out and set aside. Add a little more oil and butter to the pan. Toss in lots of peppercorns and let them cook for about 5 minutes until they start popping and become a little soft. In the meantime season your ahi tuna steak with salt and pepper. When your peppercorns have softened spread them around the pan evenly, then gently set your tuna steak on top of them and turn your steak so it can be coated with the peppercorns. Sear your tuna steak on all sides for about 3-4 minutes to achieve a nice char as your peppercorns adhere to the steak. When your tuna steak is done charring, take it out and let it rest for about 3 minutes then thinly slice it, plate it like so and enjoy!