1. Soak the skewers in water for 30 minutes (a large baking dish works well for this). Place oil, salt, pepper, cumin, aji amarillo, chili powder, thyme, and garlic in a zip-top plastic bag. Seal the bag and gently shake to combine. Add the shrimp and tomatoes, seal the bag, and then massage the outside of it to make sure each shrimp gets coated with marinade. Refrigerate for 30 minutes.
