1. Place turkey breast on a cutting board and pat dry with paper towels. Spread onion slices on bottom of slow cooker and pour in chicken broth. Rub Italian seasoning, salt and pepper on and under skin of turkey breast.
2. Place turkey breast in slow cooker on top of onion and broth. Cover and slow cook on LOW for 5 hours or until an instant-read thermometer inserted in breast registers 165 degrees .
3. Remove turkey to a clean cutting board. Cover with foil and let rest 10 minutes. Remove and discard skin; slice breast meat from bones. Cut meat crosswise into slices.