Forms don't create rows, controllers do, via calls to models. If there are few enough foods to enable you to have a checkbox for each one, then your controller can just go through the params
and create a favorite_food
entry for each one checked.
If you have more food choices that you can reasonable represent via a checkbox, then you can pass an array of choices via the form, as described in http://guides.rubyonrails.org/form_helpers.html#basic-structures