Soften the Onion: Thinly slice the red onion and place it in a small bowl. Sprinkle with salt and pour warm water over the top. Let it sit while you prep everything else, then drain and rinse well.
1 small red onion, 1 cup warm water, 1 teaspoon salt
Prep Tomatoes and Cucumber: Place the tomatoes and sliced cucumber in a large salad bowl. Drizzle with 2 tablespoons of olive oil (reserve the rest for finishing) and season with salt and black pepper. Let them sit to create a natural dressing.
3 cups fresh tomatoes, 1 medium cucumber, 3 tablespoons extra virgin olive oil, Salt and black pepper
Warm the Beans (Optional): Warm the beans gently in a small pot over low heat for about 5 minutes, just until heated through. Skip this step if you want a fully no-cook version.
1 15-ounce can cannellini beans, drained and rinsed
Combine the Salad: Add the drained beans, tuna, and rinsed onions to the tomato mixture. Gently toss everything together with your hands or wooden spoons. Be careful not to break up the tuna too much.
1 5-ounce can tuna packed in olive oil, drained
Add Basil and Serve: Tear the basil leaves and scatter them over the salad just before serving. Toss lightly again. Serve in shallow bowls with an extra drizzle of olive oil.
½ cup fresh basil leaves