Mix the onion with the lemon juice, lemon and clementine zest and garlic.
Tip the lentils into two bowls or lunchboxes and drizzle over the balsamic and 1 tbsp oil. Heat the remaining oil in a large non-stick wok, add the pepper and stir-fry for 3 mins. Tip in half the onion and cook until tender. Pile on top of the lentils, then mix the clementines, remaining onions, feta, mint and walnut pieces.
