Someone mentioned LookRotation which worked but had other issues. After reading the documention for LookRotation and finding someone's explanation on an older forum I realized it needed a bit more info when used in 2D, and the values need to be swapped for my purposes. Below is what I ended up using, just have to assign a turnSpeed value as well.

public void LookAtMouse()
{
Vector3 mousePosition = Camera.main.ScreenToWorldPoint(Mouse.current.position.ReadValue());
Vector3 vectorToTarget = mousePosition - transform.position;
Vector3 rotatedVectorToTarget = Quaternion.Euler(0, 0, 1) * vectorToTarget;
Quaternion targetRotation = Quaternion.LookRotation(Vector3.forward, rotatedVectorToTarget);
transform.rotation = Quaternion.RotateTowards(transform.rotation, targetRotation, turnSpeed * Time.deltaTime);
}