There is nothing special about serverless backend that would make one framework more suitable than another.
Serverless backend app is likely pretty small, so I would recommend a framework that’s easy to work with but has the features that you would want already included in the box.
You might want to look into Vue.js because it’s small, well documented and complete. Its light like React but has computed properties from Ember which are very helpful. It has Directives from Angular which are helpful for making your templates more expressive.
Definitely look at Vue.js