Cook rice according to package directions. Transfer to large bowl; stir in vinegar, lime zest, salt and sugar. Let cool completely. Refrigerate for 1 to 2 hours or until well chilled.
Shape 1 tbsp rice into 2-inch round; transfer to parchment paper–lined tray. Repeat with remaining rice (you should have 24 rounds).
Heat 1/4 cup oil in large nonstick skillet set over high heat. In 5 batches, cook rice rounds for 3 to 4 minutes per side or until golden brown and crispy, adding oil to the pan as needed. Transfer to paper towel-lined tray.
Meanwhile, in shallow dish, combine white and black sesame seeds. Pat tuna dry with paper towel; roll in sesame seeds to coat.
Heat oil in large heavy-bottom skillet set over high heat until smoking. Cook tuna for 1 to 2 minutes per side or until seared and sesame seeds are golden. Transfer to cutting board; let stand for 5 minutes. Slice thinly into 24 slices.
In blender, purée avocado, mayonnaise and lime juice until smooth.
If this dish has left you hungry for more crispy rice inspired ideas then look no further. Here are some other great ideas for crispy rice based dishes and how to make them.
Both rice wine and rice vinegars are popular ingredients in dishes all over Asia. Although the two have very similar names they are slightly different. Both are made with fermented rice, however they serve different purposes.
Rice wine vinegar is typically used as an alcoholic drink which can also be used for cooking whereas rice vinegar is non alcoholic, sweeter and normally used for salad dressing and pickling vegetables.
Although the two do share some similarities they also have many differences so it is generally best not to swap them. Instead try using a pale dry sherry or a dry white wine if you are unable to get your hands on any rice wine vinegar.