Coat the tuna in olive oil and season with salt and pepper.
Add the tuna to the grill and cook for about 7-8 minutes per side or until dark grill marks have formed and the tuna is cooked throughout, no pink. Place the tuna on a plate and chill in the refrigerator until completely cooled.
In the meantime, prep all the vegetables and add them to a large bowl along with the eggs, mayonnaise, mustard, lemon juice, salt, and pepper.
When the tuna is done cooling roughly mince it until it is in bite-size pieces and then add it to the bowl with the vegetable mixture.
Mix until everything is well mixed in and serve.
Notes
Chef Notes:Make-Ahead – You can make this up to 1 day ahead of time.How to Store – Cover and chill for up to 3 days. This will not freeze well.If you plan on serving this the next day, drain off any excess liquid and re-season with salt, pepper, and toss with a little more mayonnaise.You can substitute out the fresh tuna in this recipe with frozen-thawed, or even canned.Feel free to pan-sear or broil the tuna if you do not have access to a grill.