Salt and pepper the duck breasts on both sides. On top of the stove, using a large sautÚ pan over medium heat, brown the breasts skin side down for 5 minutes, moving them around to avoid sticking. Pour off the excess fat that has cooked out from under the skin, turn the breasts and cook meat side down for 3 minutes. Remove the breasts and drain. Parboil the carrots in salted water for 5 minutes, then remove and drain. In a braising pan with a tight-fitting lid, soften the tomato paste in the veal stock over medium-high heat. Add half of the Madeira and whisk into the stock. Introduce the duck breasts to this braising liquid skin side up. Cover, and set in a preheated oven at 375░F for 35 minutes. Baste the breasts several times. After 20 minutes add the parboiled carrots and continue to braise for an additional 15 minutes. When the breast meat is resilient to the touch, and soft enough to cut with a spoon (at an internal temperature of about 145░F), remove the duck breasts and carrots to a warm platter and cover with foil.
In a small bowl, soften the arrowroot in the remaining Madeira. On top of the stove, add the arrowroot mixture to the braising liquid in the pan and reduce to a stiff consistency, about 1/2 cup. In a saucepan over very low heat slowly combine the reduced braising liquid with the orange and lemon juices (or the Seville marmalade) and simmer for 5 minutes, reducing slightly. Adjust the salt and pepper to taste. At the last minute add the julienne of orange and lemon peel, but do not allow the sauce to boil beyond this point.
Slice the duck breasts across the grain, and arrange the pieces on each serving plate. Serve the carrots, glaze the duck with the sauce, and send the balance of the jus orange to the table in a sauce boat.