Add the Bellucci 100% Italian Extra Virgin Olive Oil and garlic to a small saucepan set over low heat. Salt and pepper the tuna. When the oil just comes to a very gentle simmer and the garlic starts to just turn golden, add the tuna and stir to evenly coat the fish with oil. Continue to stir and move the fish around the pan until the exterior is completely cooked, about 5 minutes. Turn off the heat and let the tuna cool in the oil. Transfer all the contents of the pan to a sealable container and refrigerate until ready to use, or up to 1 week.
Drain the tuna from the oil and give the fish a rough chop. Add it to a medium bowl along with the red onion, celery, mayonnaise, dijon, dill, salt, and pepper. Stir well to combine. Taste and adjust seasonings to your desire. Use on a sandwich or in a salad.