Prepare the chicken by removing the backbone using a pair of kitchen shears or a sharp knife. Transfer the chicken to a baking sheet and and flatten it down to spread the chicken out as much as possible.
In a blender or food processor, combine the peppers, garlic, thyme, allspice, onions, brown sugar, nutmeg, ginger, olive oil, lime juice, vinegar, salt, and pepper. Blend until smooth.
Pour the marinade over the chicken. Cover with foil or plastic wrap and marinate in the fridge for at least 3 hours or overnight.
Preheat the oven to 400°F (200°C).
Remove the foil or plastic wrap and roast the chicken for 45-50 minutes, until cooked through. Rest for 10 minutes on a cutting board before carving and serving.