1. preheat oven to 250C

2. chop pistachios to fine crumbs, mix on baking tray with lemon zest

3. cut tuna loin length-wise into 2 or 3 cylindrical pieces, 6-7 cm thick

4. brush tuna with olive oil, coarse sea salt and pepper

5. place iron skillet over high heat and allow to heat up

6. sear tuna lightly for 3-4 minutes, turning them around as you go.

7. remove tuna, cool, and brush with mustard, and roll in chopped pistachios

8. transfer to baking tray and roast for 5-6 minutes

9. serve with Papaya Salsa