• Quarter the potatoes (or otherwise cut into bite-size pieces). Boil in salted water for 15 minutes, or until fork-tender. Drain and immediately season with sea salt.
• Meanwhile, hardboil the eggs. Set aside to cool. When cool, peel and cut into quarters.
• Blanch the green beans for 2 minutes, then plunge into cold water to stop them cooking.
• Cut the tomatoes into wedges (or halves, if using cherry tomatoes).
• Pat the tuna steaks dry, then season with salt and pepper. Heat 2 tbsp. oil in a large pan over medium-high heat. Sear the tuna about 1½–2 minutes on each side, until about ¼″ of the flesh turns opaque white, leaving a thick, red stripe in the center of the tuna steaks. Turn vertically onto the edges and quickly sear edges long enough to turn white.
• Let the tuna rest briefly, then gently cut into ¼″ slices using a very sharp knife.

Vinaigrette

• Whisk together 1 cup olive oil, white wine vinegar, Dijon, sugar, salt, and black pepper. Drop in the crushed garlic.
• Let stand at least 10 minutes before serving so the garlic will infuse the vinaigrette. Stir again if it begins to separate.

Assembly

• On a large platter, lay out a bed of whole lettuce leaves. In thin stripes, lay out the toppings in any order: olives and capers, tuna, tomatoes, green beans, potatoes, and eggs.
• Serve with the dressing (as well as any extra salad ingredients that didn't fit on the platter).