Preheat the oven to 350 degrees F. Place the turkey breast skin side up in a rack on a roasting pan. You can use a lightly greased 9X13 pan as well if you do not have a roasting pan.
Combine the butter, garlic, paprika, thyme, salt and pepper together in a small pan.
Rub the butter mixture on the outside of the turkey breast using a basting brush.
Place the sliced onion on the bottom of the pan. Then place the turkey on top.
Bake for 13-15 minutes per pound (so I baked the 9 lb turkey breasts for 2 hours) until the turkey reaches an internal temperature of 160 degrees F. I use a meat thermometer to ensure that the turkey is cooked to the current temperature.
Remove the oven, loosely cover with foil and allow the turkey breast to rest for at least 5 minutes.