Steam is too hot for coffee – that’s what is meant by ‘burning’ it. It’s really scalding it, or cooking it slightly. Coffee water (unlike tea) needs to be less than boiling, around 92-95C.
The problem with the moka pot is that to get the water to come through you need pressure which would usually come from boiling the water – but that cooks the coffee.
All you really have to do is put it on a reeeeally low heat – so the water is forced through by the expansion of the air gap above the water BEFORE it boils. This does take a while, and the coffee will dribble out of the spout really slowly. If it spurts, that’s too hot. When it starts coming through you can probably take it off the heat and it’ll finish, and you’ve got no risk of over-heating then.
The resulting coffee will have gone through the grounds really slowly though resulting in an amazingly strong but still really smooth solid velvety texture – not unlike Turkish coffee but without the grit. Do not drink too much! It’s a fair bit stronger than espresso made this way.
If you damp the coffee grounds before you assemble the thing, with cold water, it seems to improve things further.