Bring a large pot of salted water to a boil, then add the halved red potatoes and cook for 10 to 12 minutes until they are fork-tender. Use a slotted spoon to transfer them to a bowl, and in the same boiling water, gently lower the eggs and cook for exactly 7 minutes before transferring them to an ice bath to cool.

Add the trimmed green beans to the same boiling water and blanch for 2 to 3 minutes until they are crisp-tender and bright green. Immediately plunge the green beans into the ice bath alongside the eggs to stop the cooking process, then drain both ingredients thoroughly.

Whisk together the extra-virgin olive oil, fresh lemon juice, Dijon mustard, minced garlic, salt, and cracked black pepper in a small bowl until the dressing is fully emulsified and smooth.

Heat a grill pan or cast-iron skillet over high heat until it is smoking hot. Brush the tuna steaks with one tablespoon of olive oil, season generously with salt and pepper on all sides, and sear for 1 to 2 minutes per side until a golden crust forms while keeping the center rare and pink.

Peel the cooled eggs and slice them in half, then arrange a bed of torn butter lettuce on a large serving platter.

Arrange the cooked potatoes, green beans, halved cherry tomatoes, olives, capers, and halved eggs in neat, separate mounds on top of the lettuce bed.

Slice the seared tuna steaks into half-inch thick slices and place them in the center of the platter, then drizzle the prepared lemon-herb vinaigrette over the entire salad just before serving.