The paste is a spice paste, which is used in me usually also as a spice. Everything braised with sauce tolerate a little of it, whether goulash, roulades, roasts, game, Chili con carne (here like more), etc.
Also homemade sauces such as BBQ sauce or sausage sauce wins, assuming you want to have focus, with this paste.
I use for cooking / grilling actually no more chillies unless whole pods are required, but only the Harissa paste.
An absolute highlight are grilled merguez sausages (African pepper Cumin and chili sausage) with harissa, either neat for very hard (thereby the tasty sausages taste almost completely goes down) or harissa and ketchup 1: 1 or even mild 1: 2 mixed (my favorite because you can taste the sausage still).
So far I could even convince many guests of the spice paste.
Just try, but watch out: Chöön chaaaaf :)