Tuna and Tomato Pizza

Ingredients

• 3 tsp extra virgin olive oil
• 1 onion (finely chopped)
• 1 398ml can chopped tomatoes
• 1/2 tsp dried oregano
• 1/8 tsp sugar
• pepper (to taste)
• 2 ready-made thick pizza bases (about 300 g each)
• 2 tbsp tomato sauce
• 1 170g can tuna in water (drained and flaked into chunks)
• 4 tsp capers
• 8 black olives (pitted and sliced)
• fresh basil leaves (to garnish)