Tuna Tartare Tower with Avocado and Red Onion

4 oz Bluefin tuna, finely diced
1 ripe avocado, diced
2 tbsp red onion, finely chopped
1 tsp soy sauce
1 tsp sesame oil
1 tsp lime juice
Salt and pepper, to taste
Optional: cilantro for garnish

1. In a bowl, gently mix the tuna with soy sauce, sesame oil, and a pinch of salt. Set aside.
2. Toss avocado with lime juice, salt, and pepper.
3. Using a ring mold, layer the avocado at the base, followed by a layer of red onion, and top with the seasoned tuna.
4. Carefully remove the mold and garnish with cilantro.