This is a full meal in a bowl: roasted baby potatoes, blistered cherry tomatoes, caramelized red onion and bell pepper, oil-packed tuna, Castelvetrano olives, capers, and peppery arugula, all pulled together with a lemon-Dijon dressing. It takes about 50 minutes start to finish, most of that hands-off roasting time. The real reason to make it is that it actually keeps you full โ the combination of roasted vegetables, quality tuna, and toasted almonds gives it enough substance to stand in for dinner.
What makes this version work
Two things matter here. First, roasting the vegetables in a single layer at high heat โ not crowding the pan โ is what gets you caramelized edges on the potatoes and blistered tomatoes rather than steamed, watery vegetables that make the arugula wilt on contact. Second, the lemon-Dijon dressing does real structural work: Dijon acts as an emulsifier, keeping the oil and lemon juice from separating so the dressing actually clings to the greens and coats the warm vegetables evenly. Dress it at the table โ a pre-dressed salad goes limp fast, especially with warm components pulling moisture out of the arugula.
Shopping notes
- Oil-packed tuna: Worth seeking out. Water-packed tuna is drier and blander; oil-packed flakes into soft, meaty chunks that hold up against the roasted vegetables. Italian or Spanish brands in jars or tins are your best bet at most grocery stores or Italian delis.
- Castelvetrano olives: These are mild, buttery, and bright green โ very different from canned black olives. Find them at the olive bar or jarred in the deli section. Kalamata olives work as a swap but will add more sharpness.
- Baby gold potatoes: Their thin skins mean no peeling and they roast faster than larger potatoes. Regular Yukon Golds cut into 1-inch chunks are a fine substitute.
- Capers: Brined capers in a jar are standard and easy to find. Rinse them briefly if you want a slightly less salty bite.
If something goes sideways
- Potatoes are still firm after roasting: They need more time. Halved baby potatoes can take longer depending on your oven. Give them 5-minute increments and test with a fork โ the cut side should be golden and the center should yield without resistance.
- Tomatoes released too much liquid and made the pan soupy: This usually means they were too crowded or the oven wasnโt hot enough. Drain off the excess liquid before adding the tomatoes to the salad, or theyโll waterlog the arugula.
- Dressing tastes flat: Add more lemon juice before oil, not after โ acidity is harder to balance once the oil is in. A small pinch of salt often fixes a dressing that tastes dull rather than sharp.
- Arugula wilted immediately on contact with the vegetables: The roasted vegetables were too hot. Let them cool for 8-10 minutes off the pan before assembling โ warm is fine, steaming hot is not.
- Almonds lost their crunch: Toast them fresh and add them last, right before serving. Almonds that sit in a dressed salad soften within minutes.
Keeping it fresh
Store components separately if youโre planning ahead. Roasted vegetables keep well in an airtight container in the refrigerator for up to 3 days; reheat them briefly or bring to room temperature before assembling. The dressing holds in a sealed jar in the fridge for up to 5 days โ give it a good shake before using since it will separate. Keep the arugula dry and undressed until youโre ready to eat. Once fully assembled and dressed, this salad is best eaten within an hour; after that the greens soften, the almonds lose their crunch, and the tuna starts to dry out. If youโre packing it for lunch, carry the dressing and almonds separately and combine just before eating.
Tuna and Roasted Vegetable Salad
Equipment
- Rimmed baking sheet
- Parchment paper
- Large mixing bowl
- Small mixing bowl
- Whisk
- Tongs or spatula
- Chef's Knife
- Cutting board
- Skillet (for toasting nuts)
- Microplane or fine grater
Ingredients
For the Roasted Vegetables:
- 1 lb baby gold potatoes halved, scrubbed
- 1 large red bell pepper cored and cut into 1-inch strips
- 1 small red onion cut into 8 wedges
- 1 pint cherry tomatoes left whole
- 2 tbsp extra-virgin olive oil for roasting vegetables
- ยฝ tsp kosher salt for seasoning vegetables
- ยผ tsp freshly ground black pepper for seasoning vegetables
For the Tuna & Salad Base:
- 10 oz oil-packed tuna drained well, flaked into large pieces
- 5 oz baby arugula washed and spun dry
- ยฝ cup Castelvetrano olives pitted and halved
- 2 tbsp capers rinsed and drained
- โ cup celery thinly sliced
- ยผ cup flat-leaf parsley roughly chopped
For the Lemon-Dijon Dressing:
- 3 tbsp extra-virgin olive oil
- 1 tbsp fresh lemon juice
- 1 tsp Dijon mustard
- 1 tsp honey
- 1 clove garlic finely grated
- ยฝ tsp lemon zest finely grated
- ยผ tsp kosher salt for dressing
- ยผ tsp freshly ground black pepper for dressing
For Finishing:
- ยผ cup toasted almonds coarsely chopped
- ยฝ tsp crushed red pepper flakes optional, for heat
Instructions
- Preheat and Prepare the Pan: Heat the oven to 425ยฐF / 220ยฐC with a rack in the center. Line a rimmed baking sheet with parchment for easy cleanup and crisp edges.
- Toss the Sturdy Vegetables: In a large bowl, combine the potatoes, red bell pepper, and red onion. Drizzle with 2 tbsp olive oil, season with 1/2 tsp kosher salt and 1/4 tsp black pepper, and toss to coat. Spread in an even layer on the prepared sheet, leaving space between pieces.
- Roast, Then Add Tomatoes: Roast the vegetables for 20 minutes at 425ยฐF / 220ยฐC until the potatoes are beginning to blister and edges turn golden. Remove the pan, add the cherry tomatoes, toss gently with the hot vegetables, and return to the oven for another 10 minutes, until the tomatoes just burst and everything is tender with caramelized edges.
- Toast the Almonds: While the vegetables roast, warm a dry skillet over medium heat. Add the chopped almonds and toast, stirring, for 3โ4 minutes until fragrant and lightly golden. Transfer to a plate to cool so they stay crisp.
- Whisk the Lemon-Dijon Dressing: In a small bowl, whisk together 3 tbsp olive oil, 1 tbsp lemon juice, 1 tsp Dijon, 1 tsp honey, garlic, lemon zest, 1/4 tsp kosher salt, and 1/4 tsp black pepper until emulsified and glossy, about 30โ45 seconds.
- Flake the Tuna: Drain the oil-packed tuna thoroughly. Using a fork, flake into bite-sized pieces, keeping some larger chunks for texture.
- Dress the Greens and Vegetables: Place the baby arugula in a large mixing bowl. Add the warm roasted vegetables and drizzle with half of the dressing. Toss gently with tongs until the arugula is lightly coated and just beginning to wilt.
- Fold In Tuna and Briny Accents: Add the tuna, olives, capers, celery, and parsley. Spoon over the remaining dressing and fold carefully to keep tuna pieces intact. Taste and adjust seasoning with a pinch more salt or lemon if desired.
- Finish and Serve: Scatter the toasted almonds and, if using, red pepper flakes over the top. Serve immediately while the vegetables are still warm and the greens are supple.
Notes
Chefโs Tips:
- Use oil-packed tuna for superior texture and flavor; if using water-packed, whisk an extra 1 tbsp olive oil into the dressing.
- For deeply caramelized vegetables, avoid crowding the panโspace promotes browning rather than steaming.
- Season in layers: salt the vegetables before roasting, then balance with the bright, lightly sweet dressing.
- Make-ahead: roast vegetables up to 1 day in advance and rewarm at 350ยฐF / 175ยฐC for 8โ10 minutes before assembling.
- Greens swap: baby spinach or little gem lettuce also work; keep greens tender to contrast the hearty roast veg.
Frequently asked questions
Can I use water-packed tuna instead of oil-packed?
You can, but the result will be noticeably drier and less flavorful. If water-packed is all you have, drain it well and toss it with a teaspoon of good olive oil before adding it to the salad to compensate.
Can I make this ahead for a dinner party?
Yes โ roast the vegetables and make the dressing up to 3 days in advance, then assemble right before serving. Donโt combine the greens, warm vegetables, tuna, and dressing until youโre ready to eat, or everything will go soft.
Is this salad served warm or cold?
Room temperature is the sweet spot. The roasted vegetables should be warm but not hot when they hit the arugula โ about 8 to 10 minutes off the pan. Serving it straight from the fridge mutes the flavor of the roasted vegetables considerably.
What can I use instead of arugula if I donโt like the bitterness?
Baby spinach is the most neutral swap and holds up well against warm vegetables. Mixed greens also work, though theyโre more delicate โ add them last and toss gently so they donโt bruise.