- Mix the fennel seeds, mustard seeds, and peppercorns in a mortar. - 1 tsp. fennel seeds, 1 tsp. mustard seeds, ¼ tsp. black peppercorns 
- Coarsely grind everything, add the sesame seeds, and season to taste with sea salt. - 4 tbsp. sesame seeds, Sea salt 
- Spread the spice mixture evenly over the whole surface of a plate and press the tuna steaks into the mixture to coat. - 4 tuna steaks 
- Heat the coconut oil in a skillet placed over medium-high heat. - 3 tbsp. coconut oil 
- Brown each tuna steak for 2 to 3 minutes per side or until they reach the desired doneness.