Preheat oven to 400F
Place onion, garlic and lemon in a casserole dish or roasting pan large enough for your turkey breast.
Add the chicken broth to the dish.
Pat the turkey breast dry with kitchen paper towel and place in the casserole dish.
Use a spoon or your fingers to pull the turkey skin away from the flesh.
Insert the butter in between the turkey skin and flesh.
Rub the poultry seasoning all over the turkey breast, then drizzle with olive oil.
Bake for 35-45 minutes, until an inserted meat thermometer reads 160F.
Allow the turkey breast to rest for 10 minutes. It will increase in temperature the remaining 5F.
Slice and serve.