Thinly slice the onion and garlic. Peel the sweet potatoes and cut them into bite-sized cubes. Slice the red pepper and halve the cherry tomatoes.
Heat the olive oil in a large frying pan or sauté pan. Add the onion and garlic and cook for about 5 minutes until softened.
Add the sweet potatoes and red pepper, followed by the oregano and chilli flakes, if using. Stir-fry for about 1 minute, then add the cherry tomatoes. Season with salt and freshly ground black pepper.
Cover the pan and cook over medium-low heat for 8–10 minutes, stirring occasionally, until the vegetables are tender. Add a splash of water if they become too dry.
Once the vegetables are cooked, add the balsamic vinegar and stir for 1–2 minutes, allowing it to reduce slightly and coat the vegetables.
Add the maple syrup and stir for another minute or so, until the vegetables are lightly glazed and slightly sticky.
Scatter with fresh coriander or parsley and serve warm.