Here are two smashing ideas for a tuna sashimi appetizer. First, you need to buy Grade A (sashimi-grade) tuna and not the lesser quality ones that are not suitable for consuming rare. The top most picture, is a pan-seared pepper tuna with wasabi and ginger aioli. The tuna is first seasoned with salt and fresh ground pepper and lightly pan seared to a medium rare to rare temperature. On a hot skillet, this should take less than two minutes. Try to cut the tuna steak into a symmetrical rectangle block. You can either season and sear all four sides or just the top and bottom. I prefer to do all four sides but it's all up to you. Once the tuna is done (which should take no time at all), set it aside and let it rest. To create the aioli topping, I start with regular mayonnaise and add wasabi powder (or paste), ginger powder and fresh garlic that has been mashed into a paste-like consistency. Season with salt and the aioli is ready to go. Now to add some crunchy texture and color to the presentation, cut some chives and red radish into tiny cubes and sprinkle on top of the aioli. And there you have it. pepper-seared tuna with wasabi and ginger aioli.For our next appetizer, this time, slice the tuna into thin slices. Lay it down on a plate and top it with finely chopped fresh ginger and scallions (or chives). Simply season it with soy sauce and a dash of lemon juice. Now, let's heat up a few tablespoons of extra virgin olive oil or sesame oil until it starts to smoke. Sesame oil has a low smokepoint, so it should start smoking rather quickly. Just spoon some of the oil over the tuna slices and see it sizzle and cook just a little, perfect for a bite-size tuna sashimi appetizer. This technique was invented by famed Japanese chef, Nobu Matsuhisa, owner of his chain of Nobu Restaurants around the world. And like most inventions, it came by accident. When a customer returned a sashimi dish because he/she didn't like raw fish, this was Chef Nobu's perfect solution to the problem. He called it New Style Sashimi. I prefer to call it Nobu Style Sashimi.