Heat oil in a large frypan over medium heat. Add onion and cook, stirring, for 3-4 minutes until softened. Stir in garlic, chilli and tomato paste, and cook, stirring, for 2 minutes or until fragrant. Add wine, tomatoes and oregano, and season. Simmer for 10-12 minutes until thick and reduced. Add lemon juice and pasta along with reserved cooking water, stirring to coat in the sauce. Scatter with extra chopped chilli, and dried chilli flakes (if using) to serve.