Lambda to create EMR Cluster don't fire the cluster creation

I'm trying to run a λ code that creates a cluster, but nothing happens, maybe I'm misunderstanding the usage on Node (since I'm not that familiar with it.)

The function is as simple as:

// configure AWS Dependecies var AWS = require('aws-sdk');

exports.handler = function(event, context) {
    // EMR Client
    var emr = new AWS.EMR({apiVersion:'2009-03-31', region:'us-east-1'});

    var params = {... dozens of params describing jobs ...};
    var AWSRequest = emr.runJobFlow(params);
    AWSRequest
        .on('success', function(response){ console.log("success => " + response)})
        .on('error', function(response){ console.log("error => " + response)})
        .on('complete', function(response){ console.log("complete => "  + response)})
        .send( function(err, data){
            if (err) console.log(err, err.stack); // an error occurred
            else     console.log(data);           // successful response
        });

    context.done(null,'λ Completed');
};

I'm testing it with the grunt-aws-lambda grunt task and in the console, but nothing shows except for:

aws-emr-lambda$ grunt lambda_invoke
Running "lambda_invoke:default" (lambda_invoke) task

Message
-------
λ Completed

Done, without errors.

Executing it from the aws console results in the same output and no EMR Cluster is created.

Any thoughts on this?