To make the tomato puree, heat the olive oil in a large saucepan, add onion and garlic and cook on a low heat until soft. Add the tin tomatoes and oregano. Season generously and simmer for 20 mins. Cool, then blend until smooth. Set aside.
Place the tomato puree on a serving plate. Drain Burrata of its water and place it on top of the puree.
Cut each tomato in half through the stem end and distribute them around the cheese. Drizzle the tomatoes and burrata generously with Extra Virgin Olive Oil and balsamic vinegar and sprinkle salt and pepper. Scatter the basil on the salads and serve.