A RESTful web app/API is just HTTP, so no specialized tools are needed to test performance (as opposed to functional testing, where specialized tools could be helpful). You basically just need to make a lot of HTTP requests and record the results.
I prefer ApacheBench to more complex tools such as JMeter. It’s very simple and easily scriptable — just write a shell script. I also find it oriented on HTTP, while tools like JMeter are designed to support simulating human usage patterns.
https://httpd.apache.org/docs/current/programs/ab.html