Heat a Dutch oven. Add the butter; cook the carrots, onion, celery, and garlic for 10 minutes or until caramelized. Add tomatoes and cook for another 2 minutes. De-glaze with red wine. Reduce down by half and add duck stock, canela, star anise, and bay leaves. Cook for 30 minutes, or until the sauce is reduced by 2/3. At this point, add the thyme and the tamarind paste. Cook for 5 minutes then strain sauce through a fine mesh sieve.
Heat a saute pan large enough to hold the two duck breasts. Season the duck breast with salt and pepper. Add it to the pan skin side down, and sear for 3 minutes. Place the pan in a preheated 400 degree oven for 5 minutes, or until the internal temperature of the duck is 145 degrees. Place 2 tablespoons of tamarind sauce on a plate. Slice the duck breasts on a bias and put on the plate, on top of the tamarind sauce.