Place your turkey breast in the slow cooker. Slice the apple. Combine the seasonings in a small bowl.
Rub the seasonings on the turkey breast, making sure to get some underneath the skin. Dot turkey with butter (again, put some underneath the skin.)
Place apple slices in the crockpot, on and around the turkey breast.
Cook on LOW for 3-4 hours, until the internal temperature reaches 165 degrees F.
**If your turkey breast is bone-in, then you'll need to cook it for 5-6 hours on low. After 4 hours, check every half hour to make sure you don't over cook it!
Let turkey rest after cooking- I like to leave mine in the crockpot on warm for 5-10 minutes, until just before we're ready to eat. I also remove the skin prior to serving- it helps keep the turkey moist, but the texture isn't the greatest after slow cooking. Slice and serve with a side of cranberry sauce!