Raycast2D - I just want to detect the border

So, Physics.Raycast just detects the exact point that the Ray ENTERS a Collider. If the origin point is already inside the collider, it doesn't detects anything.

This is the exactly behaviour I want, but with the 2D Raycast.

Physics2D.Raycast seems to detect everything, even when the raycast's origin is already inside the 2dCollider.

Is there some easy way to make the Physics2D.Raycast only detects when it ENTERS a collider?

Thanks.