Texture Key To Render Texture

var config = {
    type: Phaser.AUTO,
    parent: 'phaser-example',
    width: 800,
    height: 600,
    backgroundColor: '#2d2d88',
    scene: {
        preload: preload,
        create: create
    }
};

var game = new Phaser.Game(config);

function preload ()
{
        this.load.setBaseURL('https://cdn.phaserfiles.com/v355');
    this.load.image('bubble', 'assets/particles/bubble.png');
    this.load.image('dude', 'assets/sprites/phaser-dude.png');
}

function create ()
{
    var rt = this.add.renderTexture(400, 300, 64, 64);

    rt.draw('bubble');
    rt.draw('dude', 18, 14);
}