This Heirloom Tomato Sandwich with Tonnato is one of the simplest but absolutely most wonderful ways to eat an heirloom tomato sandwich in the summertime. I know the discourse about how tomato sandwiches should be made is *intense* (we all have opinions, and that’s ok!), but I love straying from the classic tomato + mayo + toast gospel. In this heirloom tomato toast, we are using a dilly version of the classic Italian sauce called Tonnato – and let me tell you, once you go tonnato, you don’t go back.
Tonnato tastes like tuna salad, but in sauce form. It’s light enough to pair perfectly with the tomato, but still zesty enough to be interesting, and packed with protein, so that it’s pretty filling, too. It’s a step up from your typical butter or mayo affair, and it tastes amazing.
This particular sandwich uses my homemade sourdough, but any bread will do. Just make sure it has a light texture that is easy to bite into, and you’ll be dreaming of this toast for the rest of tomato season… and then well into next summer.
Table of contents
What is tonnato?
So yes, tonnato translates to straight-up “tuna” in Italian, but tonnato SAUCE is something else entirely. Traditionally it’s made of tuna, anchovies, lemon juice, olive oil and mayo. Delicious. Here’s the thing, I’m not totally a mayo girl, and I like my tonnatos thicker than most, so I opt to sub out the mayo for cashew cream. I know, it sounds crazy, but it carries through the same emulsion while adding healthy fats, tasting just as delicious and being pretty dang good for you as well. When you look at it as a whole, this sauce is just high-protein fish, raw nuts (again, trust me!), lemon juice and herbs. How could you not want to eat it with a spoon? And believe me – you might end up wanting to eat it with a spoon.
For tonnato skeptics, think of it as an extra-salty, extra-addicting aioli. Or if you took the best parts of tuna salad and purréed it into a smooth, silky sauce. If you like tuna, you’ll love this. And even if you are a *bit* skeptical, just give it a try once. If you are a fan of the saucy-sauces of the world, there’s a high chance you’ll love zippy, creamy tonnato.
How to perfectly season your heirloom tomatoes
While this recipe focuses largely on the sauce – it is a tomato-based sandwich after all! And not just any tomatoes – the perfect, highly coveted summer heirloom tomatoes. You know, the ones so big and heavy and sun-ripened that you just want to pluck them from every farmers’ market you see? Yup, those tomatoes.
The thing is – these tomatoes are only this amazing when you season them correctly. Without a good hit of salt, they end up feeling kind of “meh.” So here’s how I like to season my heirloom tomatoes:
- Use large flake flaky salt – this stuff is GOLD. It will almost melt into the tomatoes, coaxing out their acid and sweetness all at once.
- Make sure to evenly layer the salt – get all across the surface area, with no portion left behind!
- Salt only right before you want to use the tomatoes – otherwise, the salt will pull out all the tomatoes’ excess moisture and make them more difficult to handle. So only salt right before you want to enjoy!
How to enjoy this sandwich (as a sandwich, or toast, or whatever)
What’s nice about this heirloom tomato sandwich is you can enjoy it as a sandwich on fresh, crusty bread, or you can make it into an open-face toast, or you can even flex it into a Panzanella salad of sorts. It’s up to you!
If you do make it open-faced, I suggest toasting or grilling your bread to make it a sturdy base for the thick dilly tonnato. If you make it as a sandwich, it’s much more forgiving. I tend to lean into either super soft sandwich bread (which is a treat but also dangerous, since I can eat a million slices of soft white bread), or go for a hearty sourdough, made just that morning. If I’m going really crazy, I dip into a baguette to make an uber-long, extra-tuna-y sandwich.
If you go the salad route, just thin out the tonnato with a bit of water and use it as a creamy tomato salad dressing. There are a million ways to capture these flavors, and I love to get creative with it.
And that’s everything for this Heirloom Tomato Sandwich with Tonnato!
And of course feel free to leave any questions, comments or reviews! This is the best place to reach me, and I’d love to hear from you <3
Heirloom Tomato Sandwich with Tonnato
- 1 small blender or food processor
- 1/2 cup raw cashews
- 1 cup boiling water
- 1 (5-ounce) can of tuna, packed in oil
- 6 flat fillet anchovies packed in oil
- 1 garlic clove
- 1/4 teaspoon red pepper flakes
- 1 tablespoon freshly squeezed lemon juice about 1/2 lemon
- 1/3 cup fresh dill
- Freshly ground black pepper
- Diamond Crystal kosher salt
- 1 large heirloom tomato
- 1-2 teaspoons flaky salt such as Maldon
- 4 slices sandwich bread of choice
- In a small heat-proof bowl, add the cashews and boiling water, ensuring there’s enough to fully cover them. Let the cashews sit for 10 minutes.
- Add the tuna (oil and all), anchovy fillets, garlic, red pepper flakes, lemon juice, dill and a few cracks of black pepper to a blender. Drain the cashews and add them to the blender with 1/3 cup of cold water. Blend everything together for 2-3 minutes or until it’s very smooth, but somewhat thick, like mayonaise. Taste and season with salt and peppe, but it shouldn't need much.
- Thinly slice the heirloom tomato into big, round pieces. Season the tomato with the flaky salt.
- Toast the bread, or if it's extra fresh, leave it untoasted, it's up to you. Spread a thick layer of tonnato on one slice, and layer the tomatoes on the other. Eat as soon as you can, that's when it's the best.