Combine Scotch bonnet and vinegar with a pinch of both salt and sugar in a blender. Puree until smooth. Set aside.
Heat 1 tablespoon oil in a wide, medium saucepan over high heat. Season salmon with salt and add to pan, skin side down. Cook 3 minutes, then flip salmon over and add butter. Sear salmon until lightly browned, about 2 minutes. Set aside.
Heat remaining 3 tablespoons oil in a medium saucepan over medium heat. Add onion and bell pepper and cook until translucent, stirring frequently, about 7 minutes. Add garlic, thyme, all but 1 tablespoon green onion, and curry powder and cook until fragrant, 2 minutes. Add tomato paste and cook 2 minutes, stirring to coat vegetables with tomato paste. Add coconut milk and stock to pot. Season with a pinch of salt and lemon juice and stir.
Bring sauce to a boil then lower heat to medium-low and simmer sauce until slightly thickened, 10 to 15 minutes. Add salmon to sauce and simmer 3 minutes. Spoon salmon and sauce over rice, garnish with remaining green onion, and serve with pepper-vinegar sauce.
