Heat the olive oil in a large, deep pan and sauté the onion for 3-4 minutes over medium heat until softened.
Stir in the garlic and red chilli flakes and continue to cook for another minute.
Add the tomato paste, cook for a further minute and then add the red wine. Cook for 1-2 minutes until the alcohol evaporates, then stir in the orzo. Toast it for 1-2 minutes, stirring often.
Next, add the chopped tomatoes, oregano, sugar and vegetable stock. Bring to a boil, then lower the heat and simmer for 15 minutes or until the orzo is tender. Add a bit more vegetable stock or water if it looks too thick.
Season to taste and serve immediately with crumbled feta on top if you like.