Warm Tuna Salad Niçoise

Place potatoes in a steamer basket over boiling water. Cover and steam until tender, 10 to 15 minutes. Transfer to a serving bowl, reserving steaming water. Add 1 tablespoon vinegar and 1 tablespoon oil and toss gently. Season with salt and pepper and set aside. Place green beans in the steamer basket, cover and steam until tender, 5 to 6 minutes. Remove from the steamer and set aside.

Heat 1 1/2 teaspoons oil in a nonstick skillet over medium-high heat. Add tuna and saute until the flesh is opaque, 3 to 5 minutes. Spoon tuna over potato mixture. Add the remaining 1 1/2 teaspoons oil to the pan. Add garlic and anchovies and cook, stirring, for 30 seconds. Add remaining 3 tablespoons vinegar and broth. Bring to a boil, stirring, and boil for 1 to 2 minutes. Stir in mustard. Spoon over the potato mixture. Add green beans, red peppers, capers and lemon juice and toss gently. Taste and adjust seasonings.