Drain the tuna thoroughly, pressing out excess oil or water, then flake it into a large mixing bowl using a fork until it’s light and flaky.
Thinly slice the red onion and add it to the bowl, noting the bright, sharp aroma as you do so.
Dice the roasted red peppers into small chunks, about 1 cm, and toss them into the bowl, watching for their smoky, colorful appearance.
Chop the celery finely and stir it into the mixture for a crisp, fresh texture that contrasts with the tender tuna.
Add 3 tablespoons of mayonnaise to the bowl, starting with a smaller amount and folding it in gently until everything is evenly coated and creamy.
Squeeze in about 1 teaspoon of freshly squeezed lemon juice, mixing gently to brighten the flavors and infuse a zesty aroma.
Chop the herbs finely—either parsley or dill—and sprinkle them over the salad, folding gently to distribute their fresh aroma evenly.
Optional: sprinkle a pinch of smoked paprika or capers for an extra smoky or briny flavor, folding it in carefully to avoid overpowering the dish.
Taste the mixture and adjust seasoning with a pinch of salt or more lemon juice if needed, ensuring the flavors are balanced and vibrant.
Let the salad rest for about 10 minutes at room temperature, allowing the flavors to meld and the textures to become even more cohesive.
Serve the tuna salad chilled or at room temperature, spooned onto toasted bread, atop greens, or eaten straight from the bowl for a fresh, luxurious experience.