1. Slice the courgettes in half and then down their length into quarters. 2. Place in a colander over a pan of boiling water and cover with aluminium foil. You could use a steamer instead. Allow to steam for 4-5 minutes until just tender. 3. Mix the Dijon mustard in a small bowl with the sugar. Add the red wine vinegar, lemon rind and lemon juice. Whisk together before gradually pouring in the olive oil. Season with salt and pepper. 4. Remove courgettes from the colander and place in a bowl. 5. Pour over the lemon vinaigrette and toss together with the courgettes. Scatter with finely sliced spring onions before serving. This dish can be served served warm or chilled.