In a small bowl, mash together 4 tablespoons of butter, sea salt, black pepper, garlic, rosemary, thyme, parsley, and paprika.

Use paper towels to pat dry the turkey. Rub the herbed butter over the top and sides of the turkey breast.

Grease the bottom of a 4- to 6-quart slow cooker with the remaining 1 tablespoon butter.

Layer the onion on the bottom of the slow cooker and pour the chicken broth over it.

Place the turkey breast on top of the onion.

Cover and cook on LOW for 8 hours or until a meat thermometer inserted in the thickest part of the breast registers 165°F.

Serve as is, or broil for about 4 minutes to brown slightly, if desired.