Stir in the onion and cook, 1 to 2 minutes. Add the curry powder, Scotch bonnet pepper, thyme, salt, and allspice. Stir well to coat. (At this point, if you have any browning or sticking at the bottom of the pot, use 1/4 cup to 1/3 cup water to deglaze the pot, scraping up the browned bits and allowing the water to evaporate.)