Tuna, Olive And Tomato Pasta

• 1 tbsp olive oil
• 1 large brown onion
• 800 g tin diced tomato
• 425 g tin tuna
• 1 tsp chilli flakes (optional)
• 200 g kalamata Olives, pitted
• 120 g spinach
• 1 cup peas, frozen
• 250 g wholemeal penne pasta
• 50 g parmesan cheese, shaved