Erase partition without recreating one?

I've got an external USB hdd that I wish to use entirely as a TrueCrypt volume. There was one pre-formatted partition, so I'm trying to erase that with Disk Utility. But no matter what I do or try, whenever I Erase the partition (or the entire disk), it keeps automatically re-creating a new partition.

How do I just erase the partition, without recreating one, thus leaving the entire disk empty (i.e. without even one partition) ?

To remove all entries from the GPT and MBR tables, open the Disk Utility application and do the following.

1. Select your disk.
2. Select Partition tab.
3. Set Partition Layout to "1 Partition".
4. Set Format to "Free Space".
5. Click on the Option... button and select "Master Boot Record".
6. Click Ok to close the pop up window.
7. Click the Apply button.

The image below was made just before clicking the Apply button.