How to set more than one cookie with Azure Functions?

UPDATE: Set multiple cookies using the "cookies" property in an HTTP response object

Unfortunately, this is currently a bug (first brought up in this issue). This isn't ideal, but here is a workaround you can use for now (note the additional white space in the "Set-Cookie "):

context.res = {
      status: 200,
      headers: {
          "Content-Type": "text/html",
          "Set-Cookie": "a=b; Secure; httpOnly; Path=/",
          "Set-Cookie ": "b=c="; Secure; httpOnly; Path=/",
          "Cache-Control": "no-cache, no-store"
      },
      body:
          '<HTML><BODY>RESPONSE</BODY></HTML>'
  };
context.done();