CustomApiController.cs

using System.Net;
using System.Web.Mvc;
using Foundation.ContentsResolvers;
using Sitecore;
using Sitecore.LayoutService.Configuration;

namespace Feature.Controllers
{
    public class CustomApiController : BaseApiController
    {
        public CustomApiController(
            IDefaultRenderingContentsResolver defaultRenderingContentsResolver,
            IConfiguration configuration)
            : base(renderingConfigFactory, defaultRenderingContentsResolver, configuration)
        {
        }

        [HttpGet]
        public ActionResult Organizations()
        {
            var item = Context.Database.GetItem("/your/test/item/path");
            var jsonResult = defaultRenderingContentsResolver.ProcessItem(i, renderingConfiguration)
            return Content(jsonResult.ToString(), "application/json");
        }
    }
}