Unity, hold down right mouse button to turn the camera

Question

How would I use my right mouse button to turn a player character in Unity, while only turning in the direction and speed of the drag?

The game is 3D and you should hold down right click and drag to turn the camera.

Here is the code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Control : MonoBehaviour {

public int speed;
public Transform tf;

// Use this for initialization
void Start () {
    
}

// Update is called once per frame
void Update () {
    if (Input.GetMouseButton(1))
    {
        tf.eulerAngles = new Vector3 (0, Input.GetAxis("Mouse X") * speed, 0);
    }
}
}

The code above works, but after moving the mouse in the specified direction the character jumps back to its original position and kind of does this glitchy turn while moving the mouse (keeps jumping back to original position).

Answer 1

An even better solution IMO would be to use transform.Rotate:

tf.Rotate(0f,  Input.GetAxis("Mouse X") * speed, 0f);

Answer 2

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Control : MonoBehaviour {

public int speed;
public Transform tf;

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {
    if (Input.GetMouseButton(1))
    {
        tf.eulerAngles = tf.eulerAngles + new Vector3 (0, Input.GetAxis("Mouse X") * 
speed, 0);
    }
}
}

^ I solved it, thanks @Gabriele Vierti.

Also, I can't accept my own answer for two days, someone please re answer this with the code so that I can set as the answer.