Cut tuna into ¼-inch dice and place in a large bowl.
In a separate bowl, combine olive oil, lime zest and juice, wasabi, soy sauce, hot sauce, salt, and pepper. Pour over tuna. Add scallions and jalapeño and mix well.
Halve avocados, remove seeds, peel, and cut into ¼-inch dice. Carefully fold avocado into the tuna mixture.
Add sesame seeds if using, and season to taste. Refrigerate at least 1 hour for flavors to blend.