Unable to delete partition from Utility Disk

Hi,

I unistalled Windows from my Mac, however when I checked the my storage there are two partitions in the internal drive - Windows and Untitled. I tried erasing it from Disk Utility or removing it using the "-" minus sign from the main disk, but still unable to delete any of it.

I also tried using the diskutil list, but I'm not sure what is the right commands to use to delete the partitions.

Please help! Thanks