For the pomegranate-harissa glaze: In a small saucepan over medium heat, add pomegranate molasses and harissa. Whisk to combine and warm to just below simmering.
For the turkey: Preheat the oven to 350 degrees F.
Season the turkey breast generously with salt and pepper. In a medium cast-iron skillet over medium heat, add vegetable oil. When the oil begins to shimmer, place the turkey breast skin-side down in the hot pan. Add the butter, thyme sprigs and garlic. Using a tablespoon, baste the turkey with the melted butter. When the skin is nicely browned, turn the breast and cook it skin-side up while continuing to baste. Cook in the pan for another 5 minutes, then brush on the pomegranate-harissa glaze and place in the oven for between 45 minutes and 1 hour, or until a meat thermometer reads 165 degrees F when placed in the thickest part of the breast. Remove turkey breast from oven and let rest for at least 10 minutes. Slice against the grain into 1/2-inch-thick slices and serve.