Heat the olive oil in a large, heavy-bottomed pot over medium heat. Add the remaining curry powder and stir it into the hot oil, letting it cook for about 20-30 seconds until it becomes fragrant — you'll really smell the spices bloom.
Add the reserved onions, green pepper, garlic cloves, thyme, and scotch bonnet pepper (if using) to the pot. Stir often, cooking until the onions have softened, which should take about 3-5 minutes. If the onions and peppers start to look dry, add about 1 tablespoon of water to keep them from sticking.