Step 1

Combine the thyme, basil, rosemary, marjoram, sage, salt and pepper in a small bowl to create a seasoning rub, then rub it all over the turkey breast, including the underside. Refrigerate the turkey, uncovered, for 12 to 24 hours. The skin of the turkey breast will tighten and look dry.

Step 2

The seasoned, air-dried breast needs to sit at room temperature for 30 minutes to 1 hour before slow-roasting.

Step 3

Meanwhile, cut the onion into about 8 wedges (from top to bottom), then arrange them to cover the bottom of the roasting pan. Preheat the oven to 450 degrees.

Step 4

Place the turkey breast (breast meat side up) on the onion in the pan. Drizzle the oil evenly over the breast. Roast for 15 minutes, then reduce the temperature to 175 degrees. Roast for 8 to 9 hours or until the internal temperature of the breast meat, when taken away from the bone, registers 165 to 170 degrees.

Step 5

Let the turkey rest at room temperature for 10 minutes before carving, or tent it loosely and carve several hours later.