Cut tuna into approximately 2cm cubes and season with salt and pepper to taste.
In a large frypan, add some oil, garlic and fish. Fry over medium heat until fish is cooked through and lightly browned. Transfer fish to a separate bowl keeping any excess oils remaining in frypan.
Using a pestle and mortar or separate bowl, mix mustard seeds (crushing a couple of the seeds), turmeric powder and gradually mix in 2 tbsp vinegar to create a fine paste (add more vinegar if necessary).
In the empty frypan, add 1/3 cup oil, mixed paste and chilli on medium heat for approximately a minute, stirring well.
Stir in cooked fish and sliced onion, remove from heat and drizzle with remaining vinegar and a generous amount of additional oil as required.
Enjoy in a buttered crusted baguette or serve as a main over steamed rice alongside haricot rouge.
Our family and I wanted to try something unique and came across this recipe. Oh my gosh so tasty! Easy to follow instructions and it was ready before we knew it. Great recipe, thanks!