Starting with ASM version 11.2, the ASM spfile can be stored in an ASM disk group. Indeed, during a new ASM installation, the Oracle Universal Installer (OUI) will place the ASM spfile in the disk group that gets created during the installation. This is true for both Oracle Restart (single instance environments) and Cluster installations. It should be noted that the first disk group created during the installation is the default spfile location, but not a requirement. The spfile can still be on a file system, in say $ORACLE_HOME/dbs directory.
Javid Hasanov's ORACLE Blog 