I suspect I'm going to regret this, but...

I have a normal, 4 burner domestic gas hob.

I have a large-ish (say 14" x 8") elliptical unenamelled cast iron griddle pan.

I would look to a cook a 8oz-10oz rump steak as well as possible

My goal is:
slightly charred texture/flavour on the outside
just set (i.e. no liquid blood) at the centre

My butcher normally supplies steak at around 18mm thick.

so - how to proceed?

BugBear