01 - Preheat oven to 350°F.
02 - Pat the turkey breast dry with paper towels. Gently loosen the skin without detaching it completely.
03 - In a small bowl, mix together softened butter, parsley, rosemary, thyme, garlic, and lemon zest until combined.
04 - Rub half the herb butter under the skin of the turkey breast. Spread remaining butter on top. Drizzle with olive oil and season with salt and pepper.
05 - Arrange onions, carrots, and celery in a roasting pan. Place the turkey breast on top, skin side up. Pour chicken broth into the pan.
06 - Roast uncovered for 1 to 1 1/2 hours, or until internal temperature reaches 165°F. Baste with pan juices every 30 minutes.
07 - Remove turkey from oven, tent with foil, and let rest for 15 minutes before slicing.
08 - Strain pan drippings into a measuring cup, discarding vegetables.
09 - In a saucepan, melt butter over medium heat. Stir in cornstarch and cook for 1 minute, stirring constantly.
10 - Gradually whisk in 2 cups of pan drippings or broth. Simmer until thickened, about 3-5 minutes. Season with salt and pepper to taste.
11 - Slice turkey breast and serve with the herb gravy.