Place beans in medium bowl. Add enough cold water to cover beans by 3 inches. Let stand overnight. Drain. Combine beans and stock in large saucepan. Bring to boil. Reduce heat to medium; cover and simmer until beans are just tender, about 1 hour. Drain, reserving 1/2 cup cooking liquid.

Heat 2 tablespoons of oil in heavy large skillet over medium heat. Add onion, carrots, and celery and sauté until almost tender, about 5 minutes. Add thyme and lemon peel and stir for 1 minute. Add beans and reserved 1/2 cup cooking liquid. Toss until heated through, about 5 minutes. Season to taste with salt and pepper. Remove from heat and cover to keep warm.

Heat remaining 2 tablespoons of oil in another heavy large skillet over medium-high heat. Sprinkle tuna with salt and pepper. Add tuna to skillet and cook to desired doneness, about 3 minutes per side for medium. Tuna can also be grilled.

Spoon beans onto center of each of 4 plate, dividing equally among plates. Top each with tuna steak. Spoon Sun-dried Tomato Sauce over the tuna steaks and serve immediately.

For Sun-dried Tomato Sauce: Place sun-dried tomatoes in food proccessor. Boil white wine vinegar, and black peppercorns in heavy small saucepan until liquid is reduced to 3 tablespoons, about 8 minutes. Strain liquid into tomatoes in processor and purée until smooth. Return tomato mixutre to same saucepan. Add whipping cream, chicken stock, and thyme. Simmer until flavors blend, about 3 minutes. Season to taste.