In a bowl add your mayo, sirracha, garlic powder and sesame oil. Mix together until fully blended, salt and pepper to taste. Set in aside in fridge until ready to serve lettuce wraps.
For the Tuna Steaks
Heat a grill pan over medium high heat and drizzle with a little bit of oil. While grill pan is heating (for about 8 minutes) Sprinkle your tuna steaks, on both sides, with a little kosher salt and coarse pepper. Drizzle with a little oil (rub in) and then on a large plate add your white and black sesame seeds. Press seasoned tuna steaks down onto sesame seed plate until fully covered in seeds.
Add tuna steaks to the now hot grill pan and sear for 2 minutes on both side. Remove, let sit for 30 seconds and then slice thin into long strips (the longer it sits, the more it will continue to cook).
Assembly
Place about 3 pieces of tuna in each lettuce wrap and top with a little lime juice, mango chunks, cucumber slices and onion pieces. Drizzle with the spicy sesame mayo sauce and serve.
Recipe by My Lavender Blues at https://mylavenderblues.com/sesame-crusted-tuna-steak-lettuce-wraps/