Steps
1. Pat the tuna steak dry and season both sides with salt, pepper, and chili flakes if using.
2. Heat olive oil in a skillet over medium-high heat.
3. Sear the tuna steak for about 2 minutes on each side for medium-rare, or longer if desired.
4. While the tuna cooks, combine diced avocado, tomato, red onion, lime juice, and a pinch of salt in a bowl to make the salsa.
5. Once the tuna is done, let it rest for a minute, then slice it thinly.
6. Plate the tuna slices and spoon the avocado salsa over the top.
7. Garnish with fresh cilantro leaves and serve immediately.