Bring a large pot of water to a boil. Turn the heat to low until the water is just simmering and carefully lower in the eggs. Cook for 7 to 8 minutes (this should yield creamy, not chalky, yolks) and remove with a slotted spoon. Transfer to a bowl of cold water. Salt the same pot of water and add the potatoes. Cook for 15 to 20 minutes, until tender but not mushy. Right before the potatoes are done, toss in the green beans and cook for 3 to 5 minutes, until crisp-tender. (You can cook the green beans in their own pot, but why waste the water and the energy?) Drain both vegetables together. Heat a grill pan or cast-iron skillet over high heat. Season the tuna with salt and pepper. When the pan is very hot, add the tuna and cook for 2 minutes per side, until browned on the outside but still pink in the middle. Remove and let rest for a minute or two, then slice into thin strips. Peel the eggs and slice in half. Toss the greens with enough vinaigrette to just lightly cover. Divide among 4 chilled plates or bowls. In individual piles around the lettuce, arrange the potatoes, tomatoes, olives, green beans, and eggs. Top with slices of tuna and drizzle with extra vinaigrette, if you like.