delete data from 2 different models

I'm trying to delete an account but at the same time i'd like to
delete the portals that belongs to the account.
This is what i wrote but it's not working.
how can i deal with this problem?

I have this code inside the account controller in the "destroy" method
def destroy
  @account = Account.find(params[:id])
  @portal = Portal.find(:all, :conditions => ['account_id = ?', ])
any ideas?

the error displays this:

NoMethodError in AccountsController#destroy

undefined method `destroy' for #<Array:0x47982a0>
app/controllers/accounts_controller.rb:78:in `destroy'