If not using pre-made hard-boiled eggs, place eggs in a small saucepan and cover with cold water by about an inch. Bring to a rolling boil over high heat. Once boiling, immediately remove the saucepan from heat, cover with a lid, and let stand for 10-12 minutes. Drain the hot water, then transfer the eggs to an ice bath (bowl of ice water) for 5 minutes to stop the cooking process. Carefully peel and chop the cooled eggs.

In a large mixing bowl, flake the well-drained tuna with a fork. Add the finely chopped celery, diced red onion, dill pickle relish, and the chopped hard-boiled eggs to the bowl.

Add the mayonnaise, Dijon mustard, fresh lemon juice, salt, and black pepper to the bowl with the tuna mixture. Mix gently with a spoon or spatula until all ingredients are thoroughly combined and evenly coated. Taste the tuna salad and adjust seasonings as needed, adding more salt, pepper, or lemon juice to your preference.

Divide the mixed salad greens evenly between two serving bowls. Arrange the halved cherry tomatoes and sliced or diced cucumber alongside the greens in each bowl.

Scoop a generous portion of the prepared tuna salad onto the bed of greens in each bowl. If desired, garnish with a sprinkle of chopped fresh parsley or a dash of paprika for extra color and flavor. Serve immediately and enjoy Grandma's comforting tuna bowl!