Pop the tuna fillet into the freezer for 5 to 10 minutes to allow the fish to firm up and make it easier to slice and dice.
Using a sharp knife cut the tuna into small cubes/ strips
In a bowl combine lemon juice, zest, chilli, olive oil, diced radish, salt, pepper and finely chopped fresh coriander.
Dice up the avocado and combine with the dressing
Pour the dressing and avocado over the tuna and gently mix together – as soon as the acid from the lemon hits the tuna it will begin to cook it, so you only need to mix lightly.
Have a taste, and tweak with extra lemon, olive oil and seasoning until you’ve got a good balance.
Pop the ceviche tuna into a snap lock Tupperware and you are ready to hit the beach for sundowners.
Serve with tortilla chips, melba toast or any other form of cracker.