This is a grown-up version of a grilled tuna melt sandwich with a cornichon caper aioli that will knock your socks off. 
5 from 1 vote

By Christie Vanover | Published February 12, 2021 | Last Updated April 11, 2023

Disclosure Aspire by Hestan compensated me for this recipe.

grilled tuna on baguette with arugula

Growing up, I loved tuna fish sandwiches. My recipe was pretty simple – just a can of tuna, some mayo and pickle relish. As I got older, I discovered tuna melt sandwiches. I used my same tuna salad recipe and topped it with Swiss cheese and cooked it on a griddle. 

Fast forward to today, and my grilled tuna melt sandwich game is way better and way more delicious.

It starts with fresh ahi tuna steaks. You can use thawed frozen ones, too, if you can’t find fresh.

Season them with olive oil, salt and pepper. Then, cook them on the grill over medium-high heat. I like to use my Aspire gas grill, instead of charcoal, because the cook is so fast, there’s no need to waste a bunch of coals. 

How long you grill your tuna is a personal preference. If you’re buying sushi grade ahi, you can essential eat it rare or with a really quick sear. If you’re going that route, I recommend cooking it over the sear station on the Aspire grill. 

For my tuna melt sandwiches, I prefer to cook my tuna to medium, so I cook it for about 3 minutes per side. 

Once I flip it, I add a couple slices of Swiss cheese. That’s where the “melt” comes from. 

At the same time, grill your bread. Rye is a nice choice, but so is a light, crispy baguette. Just brush with olive oil and kiss it with the heat for about 30 seconds. 


What makes this grilled tuna melt sandwich epic is the cornichon caper aioli. Cornichons are essentially little, tart pickles (or brined baby cucumbers), and capers are brined flower buds that resemble the taste of olives.

Mix those into some mayo with red onions or shallots, Dijon mustard and some salt and pepper, and you’ll have the best seafood sauce ever. 

bowls of capers, onions, cornichons

Smear a generous amount onto your grilled baguettes, and then layer on the rest of your grilled fish.

Top the grilled tuna melt sandwich with fresh peppery arugula and some fresh celery leaves.  

grilled tuna on baguette with arugula

Grilled Tuna Melt Sandwich

This is a grown-up version of a grilled tuna melt sandwich with a cornichon caper aioli that will knock your socks off. 
5 from 1 vote
Prep Time 10 minutes
Cook Time 10 minutes
Servings 4


  • 2 ahi tuna filets
  • 2 tsp olive oil
  • 1 tsp kosher salt
  • 1 tsp coarse ground black pepper
  • 1 baguette
  • 4 slices Swiss cheese
  • 1/4 cup arugula leaves
  • 2 tbsp celery leaves

Cornichon Caper Aioli

  • 1 cup mayonnaise
  • 4 cornichons chopped
  • 2 tbsp red onion chopped
  • 2 tsp capers chopped
  • 1 tbsp Dijon mustard
  • salt and pepper to taste


Cornichon Caper Aioli

  • Combine the mayonnaise, cornichons, red onion, capers and Dijon in a bowl. Season with salt and pepper to taste. Set aside.

Grilled Tuna and Bread

  • Rub the tuna filets with olive oil. Season both sides with salt and pepper.
  • Cut the baguette to the length of the tuna filets. Slice in half. Brush the cut sides with olive oil.
  • Heat the grill to medium-high heat. Grill the tuna for 3-4 minutes. Flip. Top with 2 slices of cheese. Grill 2-3 more minutes.
  • Place the oiled side of the baguette on the grill and grill for 30-60 seconds, until toasted.


  • Spoon a generous amount of aioli on both sides of the baguette.
  • Add the grilled tuna filet to the bottom half.
  • Top with a combination of arugula and celery leaves.
  • Add the top half of the baguette.



If you have time, make the Cornichon Caper Aioli in advance. The flavors develop nicely after 30-60 minutes. You can save it in the fridge for 1-2 weeks. It goes great with any seafood.


Calories: 695kcalCarbohydrates: 21gProtein: 29gFat: 54gSaturated Fat: 11gTrans Fat: 1gCholesterol: 71mgSodium: 1322mgPotassium: 323mgFiber: 2gSugar: 2gVitamin A: 2105IUVitamin C: 1mgCalcium: 186mgIron: 2mg

This estimate was created using an online nutrition calculator

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