Using a sharp knife, cut the tuna into very small cubes of approximately 1/4" and place them in a large mixing bowl, along with the rest of the ingredients. Stir until well combined, taste and adjust seasoning as needed.
Place a 3-3/4" round cookie cutter directly onto a serving plate and fill it with about half of the tartare mixture, then flatten the top by pressing it down firmly with a spoon or better yet, a flat object.
Remove the ring and repeat with the rest of the tartare mixture; serve immediately or cover loosely with a plastic film and chill until ready to serve, no longer than 12 hours.
At the moment of serving, garnish with a few slices of avocado, a pinch of microgreens and a few drops of toasted sesame oil.
Put the dry bulgur in plenty of cold water and place it in the fridge to soak overnight, then drain it really really well before adding to your tartare mixture.