I made tuna confit about a month ago and I used the recipe from Nosrat's book. I modified it a bit but it involved using a Dutch oven at 150ºF for about 9 min after preparing oil infused with various aromatics.
After reading Modernist Cuisine, I decided to try it again, but with the sous vide instead. The cool thing that I learned from Modernist Cuisine was that I could use glass jars which could be used to refrigerate the tuna after it was done.
I read various recipes that seemed to have different opinions on whether the product of tuna confit specifically and confit in general was pasteurized and could last for months, weeks or just days. I fine Modernist Cuisine to be the most conservative so I'll go with them - only keep the tuna for a few days.
The Modernist Cuisine recipe was pretty straight forward - brine the tuna with salt and sugar for 24 hours. Rinse the tuna, put it in jars and sous vide at 124ºF for a hour or so until the internal temperature of the tuna is 122ºF. Modernist Cuisine doesn't add any flavor to the tuna so I decided to experiment with one jar including oil infused with black peppercorns, garlic and rosemary.
The tuna came out nice although the surface of the tuna had little "growths" that looked some something in a petri dish - probably the liquid from inside of the tuna seeping out. The aromatics infused oil tasted better than the plain oil. The tuna was a bit salty - it could have been that I used sea salt that had a higher salt density than the kosher salt. I think I'll try using less salt next time.
Overall it was very nice. I served it with my alioli sauce that went very well with it. I served it for dinner, but I think this tuna is probably a better lunch or breakfast dish - maybe in a sandwich, in a salad or on the side of something else.
I summarized my current recipe that I'll try next time - Tuna Confit.