Asian flavours work extremelly well with Tuna steaks in my opinion. So to improvise a good marinade for this fish is a good idea.

One important point is to use sustainable Tuna. A second one is to make sure that the marinade don't turn your fish grey, so to not let it there too long despite Tuna being a rather fleshy fish you don't want it to become too mushy. However it can also be an option if it is the texture you are aiming for.

Then  you have to decide how to cut or eat your Tuna. This fish is so versatile. You can utilise it in a carpaccio.  Slice the Tuna very thinly in that case. There are multiple ways to flavour that dish with a marinade. If you take the Far Eastern Asia route, I would aim for the juice of a lime, a good soya sauce, or a Thai fish sauce, Sesame oil, grated ginger, sliced red chillies which you can keep for the decoration of the plate (Seeds removed or not, it depends on how spicy you want it to be at the end of the day). Even spicier you can add a dash of Wasabi sauce which resemble a little to Worcestshire sauce in power (less is more in that instance) appart if you want a lovely kick of heat). To great effect as a starter, I would say rather than a main course, depite myself not being called a Gargantua, it is a crowd pleaser especially when you take a nice care of the presentation of the dish. I would garnish it as I said with nice contrasting sliced red chillies, Lime zest could be a little plus added for decoration as well as taste, some nice peppery watercress leaves (Big, mini or micro) gives the starter a wow factor and it doesn't count just as a carpaccio any longer it is an elevated one. Even for more oumph you can pickle some Mooli radishes, (They do grow easily in winter). Thinly sliced, you can put them in the same marinade as the Tuna or prepare a similar marinade for them with the addition of crushed Sechuan Peppercorn. If your guests like a bit of heat to hit their tongues they will be in heaven. The white Mooli add interest on a plate as well as flavour and can be a great topic of conversation if one didn't know what that beautiful root vegetable was beforehand around the table.

Staying in the realm of Carpaccio with Tuna, then one can go all the way a little Italian the big way with love. After all the dish was created in Italy and enjoyed a popularity world wide with many interpretations out there which would not displeased the artist it was named after: Vittore Carpaccio. Red and White were his colours of choice and that dish needs to be a pleasure of taste to watch on the table. Thin slices of Tuna arranged artfully upon a plate which were marinated with, a little, in good Sicilian Lemon juice, a dash of Balsamic vinegar, and a dash of virgin Olive oil. Seasoning of course, Sea Salt and Black or White Pepper in this instance work. Keep it simple but you can be a little bit of a Jackson Pollock on that one to use your creativity. Imagine serving this dish, a beautifully marinated Tuna, (Red), a yogurt sauce spiked with lemon juice and white pepper, (White) drizzled upon it in a way an artist does. A quatered lime for the green to go along with some micro leaves of Watercress to get the full Italian flag on the plate in an artistic way. Pollockian yes so add the little extra some capers for more texture and a zing in your mouth which will make you sing that the moon was a big pizza pie in the night sky and it was simply Amore... You can dash in a little grated Parmesan to fly over the stars and beyond. Remember this is not bollocks it is Pollock, it is Carpaccio, and it is being creative in the kitchen like Vittore Carpaccio was. For a little extra: dicing a tomato or two very thinely along with chopped red spring onions, olive oil and seasoning on the side gets you an extre plus of winking from your guests.

Going back to marinating Tuna and how you can use it to maximum effect. Going back to the far East ways there is of course the clever treat that is sushi. This is an art in itself. In that instance I will recommand either the use of a dash of rice wine, or a little rice vinegar in the marinade. If it is a little slice of marinated Tuna upon a rectangular sushi rice the pleasure is as equaled if it was rolled in Nori sheets, along with very finely sliced cucumber and Spring Onions. It kissed your mouth.

From childhood I always considered Tuna as a fish in a tin. It was not downgraded in my mind by a long shot. I absolutly enjoyed the Tuna, Tomatoes and cold rice salad covered by chopped Parsley on summer days. Giving a twist on things, you always can do excellent salads for the summer with marinated fresh Tuna. It is a must try, and simple. Usually I use, the juice of a Lemon, Spring Onions, a little Olive Oil, a little vinegar (I tend to go for the white wine vinagar in that instence), seasoning simple salt and pepper, chopped parsley, and chopped chives. The salad I do is with baby boiled potatoes instead of rice. Diced tomatoes goes in as well as hard boiled eggs, a fresh salad of your choice, may it be rocket leaves if you want it peppery, may it be Spinash if you want to listen to your Doctor (Who seen Popeye very often in his chilhood)... Caramelised chopped Shallots or raw ones or marinated ones simply does add to the dish and you have a lovely Summer salad with nice chunks of Tuna in it. I would say don't forget the parsley and a good dressing of your choice. Or you can use the marinade by boiling it and reducing it down.

A nice combinaison with Tuna is sweetcorn so you can create a salad going the Mexican way: Por Favor Si Signor! For the marinade of your fish, you can use the juice of two limes, one peeled crush garlic clove, add crushed black peppercorn, sea salt, a dash of red wine vinegar, a chopped Jalapenos chilli pepper, last but not least chose either a neutral vegetable oil, a corn oil, or a peanut oil (Mind peanut allergic people though) or a chilli infused oil which can give that Mexican kick or the feel of a Mexican Wave across your palate. I will advise to flake the Tuna prior to put it in this spicy Marinade. 10 minutes will give you nice results but 15 will cook your fish thoroughly because of the acidity level in there.

This will give you the time to prepare your veg. For the sweetcorn, you can go for the cold version just using a tin or my prefered one is to cook the sweetcorn  cob 'En papillote' in salted butter with a good dash of Paprika, chopped Coriander/cilantro, and sliced Spring onions. You can also add a sliced Guajillo Chilli pepper at that step which is rather fruity and has a low heat intensity in the Papillote which looks like a little parcel or a bonbon. Wait until it cool enough to handle and remove the corn from the cob safely with a knife and put it in a large salad bowl ready for a salad feast. So prepare as many cobs needed for it. As a rule of thumb I would say one to two cobs per guests or every member of your family around the table. Keep the inside of the parcel to pour over the corns in the salad bowl because it is full of yumminess .

I tend to add at that stage some Sweet Bell Red Peppers, chopped, the colour add to the appeal of the salad, they can either be grilled, chard a little or eaten raw. A little more chopped Coriander and Spring Onions ( I rather like the red ones in this salad) are to be added. If you can get Tomatilloes or Cherry Tomatoes, sliced in half, it will give an extra juicy flavour which goes well with dish. Then avocadoes, diced, will bring a soothing creaminess to this little spicy number but also more vibrant colours. To say Hariba! Hariba! and to keep the fresh colour of the avocadoes so they looks like the colour of Green Gold, the purest green just splash a little lime juice in the process upon them.

Now, comes the last steps, the Marinade can end up in a very lovely dressing but you must separated it from the Tuna flakes first with a sieve. Put the flakes in the salad with all the peppercorns and marinated Jalapenos Chilli Peppers (Word of caution don't touch with your hands, drop in the salad). Bring your Marinade to a boil to reduce, then pour it in your salad bowl. All there is to do now is just stir and enjoy a bit of a Mexican Heat Wave... 

https://www.youtube.com/watch?v=Z93croz945s 

Last but not least, Tuna as a Steak can make a perfectly awesome Main meal. And the star of the show is Marinated Fish! Confession for confession, for serving a Tuna Steak I tend to go either the Eastern Asian way or the Medditeranean way. For getting to the Med' I keep it very simple for the Marinade. It is only Juice of a large Sicilian Lemon, nice Virgin Olive Oil, a dash of Balsamic Vinegar, a crushed peeled Garlic clove, Seasoning: Sea Salt and Black Peppercorns. You can add a lovely and tasty Epelette Pepper in the Marinade. A nice side to the then grilled Tuna steak or BBQ steak is roasted meditteranean vegetables, or BBQ some Veg skewers: Tomatoes, Sweet Peppers, Large Mushrooms (Portobello quartered, or Chestnut Mushrooms), Zucchini/Courgettes, Aubergines... Grilled Halloumi cheese could accompany the dish as well. This version is very summery, it is when you can feel your way singing above a BBQ 'It is Summertime'. 

For the Eastern Asian way, the Marinade consists of Dark Soya Sauce, Spring Onions sliced, Golden Caster Sugar, Rice Wine Vinegar, Grated Ginger and a couple of minced Garlic cloves. As the Tuna Steak is pan fried, you can use a nice infused oil with Chilli. To serve, I tried that recipe with a side of Jasmine Rice, Edamame Beans and more chopped Spring Onions. The same it is usefull to know that you can reused a Marinade back as long as you boil it. It will be a flavoursome sauce then. This is my last little tip.