If you live in Malaysia or Thailand then it's pretty common to see this dish pretty much in every Thai or Malaysian-Thai hybrid eateries - I mean, it is the mother of all steamed fish recipes. It's spicy and acidic in the best way possible, and you'll keep eating it even as your stomach develops an ulcer and that your tummy feels a weird kind of warm afterwards. 
Although there are so many restaurants that do this well, sometimes when I am in hermit-mode, I like to make this at home and eat it at my leisure without the need to put on pants.  The key to this recipe's success is that the fish has to be FRESH. SUPER FRESH. Otherwise, don't do it.

What You Need:
1 medium-sized, FRESH AF seabass, scaled, gutted and cleaned (dude just get the fishmonger to do it)
1 handful leafy Asian greens
1 tomato, quartered
4 cloves of garlic, peeled
5 bird's eye chili
1 inch ginger
3 large limes, juiced
Equal amount of fish sauce to the lime juice
​1 tsp sugar
1 tbsp chicken stock
Some chopped coriander

What You Do:
1. Get your steamer out. Lay our the vegetables, and place the fish on top of it. Stuff that fish with quartered tomato. Steam that fish for 15-20 mins.
2. In a pestle and mortar, pound the garlic and chilies together until you get a coarse paste.
3. In a small pot, heat the chicken stock, 1 cup water, lime juice, fish sauce, sugar and the garlic-chili paste until everything is mixed and heated through. Check for taste. It should be sharply acidic, with a nice balanced taste of fish sauce, and some heat. Add more of any of the ingredients if necessary.
4. When the fish is thoroughly cooked, remove the plate onto the table. Pour over the sauce onto the fish.
5. Garnish with the copped coriander.
6. Enjoy, but also don't foget the Gaviscon/Tums for later, just in case.

Fish scares the shit out me. For one, I come from a household where fish is usually eaten with rice, and so any other variation is not as familiar to me. Second, they are so damn delicate. Unlike chicken or meat, they break easily in the pan, and if you buy them at the wrong places they tend to smell fishy and downright gross.
But the thing is, fish is so much better than meat. Just as much protein, but with a lot less fat. Due to these reasons I have taught myself again and again to try and cook fish, and hey! Turns out, it really isn't all that hard or scary. 
Tuna tataki sounds like some fancy dish that you eat in a Japanese restaurant so fancy that you need to pay everything with a credit card and pay it off in 3 consecutive months, but no. With simple ingredients that you probably already have at home, all you need is a piece of tuna steak, which I get from my neighborhood Cold Storage for RM15. You don't need a credit card for that.
This recipe makes a plate for 1.

What You Need:
For the tuna...
1 piece tuna steak (it doesn't really matter how big)
1 tsp dijon mustard
2 tsp olive oil
2-3 tbsp coarse ground black pepper
For the soba noodles and broccoli...
1 handful soba noodles
Broccoli, cut into long florets
1-2 tbsp sesame seeds
1 small piece ginger, peeled and grated
2 tbsp light soy sauce
Some chili flakes

​What You Do:
1. First, get some water boiling in a pot on the stove. Wash and slice the broccoli into long florets.
2. Now, the tuna. Scatter the coarsely ground black pepper onto a dry, flat plate. Mix the mustard and oil, and season really well with salt. Brush the sides of the tuna with this until well-coated.
3. Now roll that tuna onto the peppercorns, so that the tuna is now crusted with them.
4. Heat a pan to high, and toast the sesame seeds until golden. Remove the seeds.
5. In the same pan over high heat, sear that tuna steak. This takes a really, really short while. Really. Like 50-60 seconds each side ONLY. Remove the fish onto a cutting board.
6. When the water begins boiling in the pot, add the soba noodles and the broccoli. Remove after 3 minutes, or until soba is cooked through. 
7. Mix the ginger, chili flakes and soy sauce. Dress the noodles with it. Add the sesame seeds to the noodles. Spoon some of the dressing over the broccoli.
8. Slice up the tuna steaks really thinly, and serve with the noodles and broccoli.
9. Keep that credit card of yours for some other day.