This particular sandwich has been continously evolving since I first started experimenting with tuna melts. I always hated celery and other crunchy veggies in my tuna sandwiches, but I've discovered that if I sauté the veggies before adding them to the tuna, the result is a much more pleasing flavor and texture (I also peel the celery like Jamie Oliver does because I'm picky like that).
Technically, you can serve these hot or cold, though I prefer the warm "tuna melt" version. To serve the tartine cold, make the tuna salad and then refrigerate it for at least half an hour before serving, and then make sure to toast the bread. To serve it hot, there is no need to refrigerate the salad - just spread it on the bread, layer tomato slices and sprinkle with cheese, and then throw them under the broiler to heat everything through and melt the cheese (see below).
I really want to make an appetizer version of these, kind of like tuna crostini, with toasted or grilled baguette slices. I think they would be great for a cocktail party.
Very Veggie Tuna Tartine (Makes 4 tartines, 2-4 servings)
4 slices whole grain bread
1 teaspoon olive oil
2 celery sticks, peeled and finely chopped
1/2 small yellow onion, finely chopped (about 1/2 cup)
1 handful (1/3-1/2 cup) finely chopped or shredded carrots
1 handful fresh spinach
1 5 oz. can of albacore tuna packed in olive oil
2 Tablespoons nonfat or low-fat Greek yogurt
1 teaspoon Dijon mustard
1 Tablespoon Vegenaise or regular mayo
1 Tablespoon capers, drained (optional)
4-5 bread and butter pickles, minced (plus extra for serving)*
4 tomato slices
Salt and pepper
1/4 cup grated Cheddar or Gruyere cheese (optional)
*You can substitute gherkins for the bread & butter pickles if you have those on hand or prefer them. Depending on the size, you'll want to finely mince 1-2 gherkins pickles.
Preheat the broiler. Use either a nonstick crisping pan (the kind you make pizzas on), or a baking pan with parchment or foil sprayed with cooking spray.
(Below are instructions for the warm version of this sandwich. If you'd like to just make a cold tuna salad tartine, complete steps 2 and 3, toast the bread in a toaster, and then add a tomato slice on top.)
1. Place the bread slices on the pan and put them in the oven to toast for about 4 minutes, even if the oven isn't completely preheated yet. You want them to be slightly toasted so that they can hold up when you put the tuna salad on them, but you're going to bake them again, so don't brown them too much the first time.
2. Heat a medium-sized nonstick pan over medium heat. Add the olive oil and sauté the vegetables until they are tender and the onion and celery become sweet. I start by adding the onion and celery and let them cook for 3-4 minutes. Then I add the carrots and let them cook 2-3 minutes, and finally add the spinach and cook it for a couple minutes, until it wilts and some of the liquid cooks off. Allow the cooked veggies to cool a couple minutes before adding them to the tuna mixture.
3. I like to start preparing the tuna mixure while the veggies are cooking. Drain most of the oil from the tuna can and add the tuna to a medium-sized mixing bowl. Add the yogurt, mustard, mayo, capers, and chopped pickles to the bowl and mix to combine the ingredients and break up the larger chunks of tuna. Add in the cooled veggies and mix to combine. You want the veggies to be evenly distributed, but don't overmix the salad. You still want there to be visible pieces of tuna when you bite into the tartine. (Refrigerate at this point if you want to make a cold tuna tartine)
You could easily eat 2 of these for a filling lunch or light dinner, but you could also pair one of them with soup or salad and stretch the dish to 4 servings.
Nutrition facts will vary depending on the veggies that you add to your tuna salad, the bread, the cheese, etc. Check out this post for an idea of the nutrition facts in a more traditional tuna salad.