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.
Our specialty Mahatma® Short Grain Rice for Sushi is ideal for these crispy rice canapés and anything requiring that compact and sticky rice texture of sushi. Try more varieties created by Mahatma® Rice that are ideal for classic rice dishes such as our Medium Grain Arborio Rice for Risotto recipes or our Parboiled Medium Grain Rice for the perfect paella recipe.
Explore more of our delicious recipe ideas and products to make all of your classic family recipes, too like Mexican rice in an Instant Pot.
For a quick and easy variation, substitute smoked salmon for tuna.