Start by washing and dicing the large cucumber into bite-sized pieces. Finely chop the red onion and any fresh herbs you are using, like dill or parsley. Drain the canned tuna thoroughly to avoid excess moisture.

In a medium mixing bowl, combine ¼ cup of mayonnaise or Greek yogurt, 1 tablespoon of olive oil, and 1 tablespoon of lemon juice. Sprinkle in ½ teaspoon garlic powder, ½ teaspoon salt, and ¼ teaspoon black pepper. Use a whisk to blend the ingredients until smooth and creamy.

Gently fold the drained tuna into the dressing until evenly coated. Add the diced cucumber, chopped red onion, and herbs to the bowl. Carefully mix everything together with a spatula.

Cover the bowl with plastic wrap or transfer to an airtight container, then refrigerate for about 20-30 minutes.

Once chilled, give your cucumber tuna salad a gentle stir and serve it cold.