Hi Valter Miranda ,
First you have to check the rule in Transaction PFAC. You have to create separate method and have to use the same logic from rule to get all approvers.
Then you have to get email ID's of all users in the same method and you have to bind the Task container to workflow container. Both containers should be multiline, so that you can append multiple email id's to a single container.
Finally you have to create send mail step and you can assign the email container to this send mail step. So that it will send emails to all approvers at the same time.
Thanks,
Vijay.