Preheat your oven to 400F and line a baking sheet with parchment. Place the potatoes on the baking sheet and drizzle them with 1 1/2 tablespoons olive oil. Mix them with your hands to coat them evenly in the oil. Sprinkle the potatoes with salt, pepper, and thyme or Herbs de Provence. Roast for 30 minutes, or until the potatoes are golden brown and easily pierced with a fork.
Bring a medium pot of water to boil. Add the green beans and boil for 3-4 minutes, or until they're tender but still firm. Remove the green beans from the water with a slotted spoon.
Add the lentils to the boiling water. Boil for 25-30 minutes, or until the lentils are tender but not mushy. Drain the lentils thoroughly through a fine sieve.
Transfer the lentils to a mixing bowl. Add 1 1/2 tablespoons olive oil, the shallot, the capers, the parsley, and the vinegar, as well as Kosher salt and black pepper to taste.
Whisk together the vinaigrette ingredients till smooth and emulsified.
Arrange a platter or individual plates with a layer of butter lettuce or baby greens, potatoes, cooked green beans, tomatoes, and the seasoned lentils. Drizzle the vinaigrette over the salad. Enjoy.