Hi Susana, please see a previous discussion on Gender and Evaluation community on this topic http://gendereval.ning.com/forum/topics/gender-audits-in-government...
Let me know what do you think. Warm greetings!
You may look at the 12 Box framework, and see if it helps. A summary of the same is attached, with reference to the full document. This framework was used by Oxfam Novib
UNDG developed a Gender Scorecard - you will have adapt it to NGOs. Reference is included on the full version.