Open both cans of tuna and pour the contents into a fine-mesh strainer set over a bowl or sink. Press the tuna gently with a clean kitchen towel or the back of a spoon to remove excess water and oil, which prevents the salad from becoming watery or overly rich.

In a medium mixing bowl, add the Greek yogurt, mayonnaise, and Dijon mustard. Stir them together until smooth and well blended, creating a creamy base that will coat all the other ingredients evenly.

Pour the fresh lemon juice into the creamy base and stir well, mixing it thoroughly throughout. Lemon juice not only adds brightness and flavor but also helps prevent oxidation and keeps your salad fresh longer in the refrigerator.

Add the drained tuna to the bowl and gently fold it in with a rubber spatula, breaking it into bite-sized pieces as you go. Avoid overmixing, which can turn the tuna into a paste instead of maintaining its flaky texture.

Stir in the finely diced celery, distributing it evenly throughout the mixture. Celery adds crunch that contrasts beautifully with the creamy base and keeps every spoonful interesting.

Add the diced red bell pepper and fold it in gently until well distributed. Bell pepper contributes sweetness and color while adding nutritional value without any additional calories from fat.

Mix in the minced red onion and chopped fresh parsley, stirring until they're spread throughout the salad. These ingredients bring a fresh, aromatic quality that elevates the entire dish from simple to sophisticated.

Taste the salad and add salt and black pepper according to your preference, keeping in mind that flavors develop and deepen as the salad sits. Start with a light hand since you can always add more, but you can't remove it once it's mixed in.

For best results, chill the finished salad for at least 30 minutes before serving to allow flavors to meld and make eating it more enjoyable. Serve cold and enjoy on greens, bread, or straight from the bowl.