Shiso and daikon cress are available at some specialist Asian grocers; substitute a mix of rocket leaves and mixed soft herbs if unavailable.
For the tuna, place all the spices into a grinder and grind to a fine mix.
Roll the tuna in the spice mix, coating all sides.
Heat a frying pan until hot then sear the tuna on each side for 30 seconds. Remove from the pan and roll tightly in cling film and place in the fridge.
For the avocado purée, peel and stone the avocado then place into a food blender with the lime juice and Tabasco and blend until smooth. Season to taste with salt and freshly ground black pepper and set to one side.
For the salad, place the apple, radishes, shiso and daikon cress in a bowl and toss to combine. Season with salt and freshly ground black pepper and stir in the olive oil.
To serve, divide the avocado purée between two serving plates.
Remove the tuna from the fridge and remove the cling film. Cut the tuna into 5mm thick slices, season with salt and pepper and place 3-4 slices on each plate. Pile the salad to one side of the tuna and serve.
