Put the eggs in a saucepan and cover with cold water by 2 inches. Bring to a simmer over medium-high heat and cook 8 minutes. Remove with a slotted spoon to a bowl of ice water to cool, then peel and slice.
Meanwhile, put the green beans in a microwave-safe bowl with 1/2 cup water and a pinch of salt. Cover loosely with plastic wrap and microwave until tender, 2 to 3 minutes. Drain and rinse under cold water. Cut the green beans in half.
Drain the tuna and toss with the green beans, scallions, bell pepper, parsley, olives, lemon juice, 3 tablespoons olive oil, 1/4 teaspoon salt, and pepper to taste.
Lightly toast the bagels. Layer the tomato slices, tuna salad and hard-boiled eggs on the bagel bottoms. Drizzle with olive oil and close with the bagel tops.
Photograph by Antonis Achilleos
Courtesy of Food Network Magazine