Cook quinoa according to packet instructions. Quinoa can be cooked and refrigerated a few days in advance. If using frozen quinoa, thaw before using.
Chop the sun-dried tomatoes into approx 1 cm pieces.
Heat olive oil in a large pan and add sun-dried tomatoes, onions, garlic and chilli flakes. Cook until the onions lightly brown around the edges, about 5-7 minutes.
Add tomato purée, olives and salt. Cook over a high heat until the tomato purée thickens significantly.
Tip the cooked quinoa into the pot and stir to combine. Taste and adjust seasoning. Add chopped basil leaves if using and stir through.
Crumble the feta over the top and serve. Can be eaten hot or at room temperature.