How to remove partition on SD card using a Mac?
The diskutil command on macOS is incredibly powerful and can do all that you need. (You can run the following in the Terminal app.)

Find your SD card:

$ diskutil list

...or:

$ diskutil list external physical

On the right, under IDENTIFIER, you'll see your disk labeled like disk2 or disk3, etc. You can use that label to reference your SD card from now on. I'm going to use disk2 for my example commands, but make sure you use your actual identifier.

For a board like the Raspberry Pi, you'll want FAT32 with MBR (Master Boot Record). Run:

$ diskutil eraseDisk FAT32 RASPBIAN MBRFormat disk2

...making sure disk2 is your SD card identifier from earlier. RASPBIAN can be anything. It'll name the Volume, which is what you'll see once it's mounted. The eraseDisk command will handle unmounting and remounting of the disk, so you don't need to worry about that.

That should be all that you need. You will end up with one FAT32 partition. It will look something like the following if you run diskutil list external:

/dev/disk2 (external, physical)
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *15.8 GB    disk2
   1:                 DOS_FAT_32 RASPBIAN                15.8 GB    disk2s1


You can then copy over the Raspbian NOOBS files to the SD card.



If you want to fully zero out or randomize your SD card, you can run:

$ diskutil unmountDisk disk2

...and then:

$ diskutil zeroDisk disk2

...or:

$ diskutil randomDisk disk2

(The zeroDisk/randomDisk command seems to prefer an unmountDisk command beforehand.)

Afterwords, you'll need to run that eraseDisk command from earlier to format it in order to be able to use the SD card.

Many other commands are available. Run man diskutil to see them all (q to quit the manual page).