WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata, 2004 Mazda MX-5 Miata, and 2003 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
Hold the camshaft by using a wrench on the cast hexagon as shown, and loosen the camshaft pulley lock bolt.