Bring a large pot of salted water to a rolling boil. Add the pasta and cook until al dente according to package directions—about 8–10 minutes. Drain and rinse under cold water to stop cooking and cool the pasta for the salad.

While the pasta cooks, whisk the dressing. In a medium bowl combine mayonnaise, Dijon mustard, lemon juice, dill, a pinch of salt, and a few grinds of black pepper. Taste and adjust—this dressing should be bright and slightly tangy.

Flake the drained tuna into a large mixing bowl with a fork, keeping some chunkier pieces for texture. Add the halved cherry tomatoes, diced cucumber, red onion, and peas.

Add the cooled pasta to the tuna-vegetable mix. Pour the dressing over the salad and gently fold until everything is coated—be tender here so the tuna keeps its flaky texture.

Chill for at least 15–20 minutes to let flavors marry; it tastes even better after an hour. If you’re serving immediately, a brief rest still helps the dressing settle into the pasta.

Finish with fresh dill, a few turns of black pepper, and optional capers or olives. Serve slightly chilled or at room temperature.