Prepare the Potatoes: Place the baby potatoes in a large pot of salted water. Bring to a boil and cook until fork-tender, about 10 to 12 minutes. Drain and let cool slightly, then slice.

Blanch the Green Beans: Cook the green beans in boiling water for 3 to 4 minutes, then transfer to an ice bath.

Boil the Eggs: Place eggs in a saucepan, cover with water, bring to a boil, cover, and remove from heat. Let sit for 9 minutes, then peel and slice.

Whisk the Vinaigrette: Combine olive oil, lemon juice, Dijon mustard, minced garlic, salt, and pepper in a bowl and whisk until emulsified.

Assemble the Base: Arrange fresh greens on a platter and drizzle with a small amount of dressing.

Layer the Components: Arrange potatoes, green beans, tomatoes, radishes, and olives on top of the greens.

Add the Protein: Flake tuna into chunks and place in the center, arranging egg halves around it. Sprinkle capers over the salad.

Final Garnish: Drizzle remaining dressing over the salad and garnish with fresh herbs if desired.