1.Make thyme dressing. Combine ingredients in screw-top jar, shake well.
2.Cook lentils with thyme sprigs, uncovered, in large saucepan of boiling water until tender, drain lentils, discard thyme sprigs. Place lentils in large bowl with half of the dressing, toss gently to combine.
3.Meanwhile, discard leaves and most of the stalk of each beetroot. Boil, steam or microwave unpeeled beetroots until just tender, drain. When cool enough to handle, peel beetroots, cut each beetroot in half.
4.Cook sausages in heated large non-stick frying pan until browned and cooked through. Cool 5 minutes, slice thickly.
5.Reheat same pan, cook onion, seeds, cumin and coriander, stirring, until onion softens. Add stock, bring to a boil. Remove from heat, stir in spinach.
6.Add spinach mixture, beetroot, sausage and remaining dressing to lentil mixture, toss gently to combine.
Merguez sausages, from North Africa, are traditionally made with lamb and seasoned with garlic and hot spices. They can be found at most delicatessens and sausage specialists. Golden beetroots have a slightly sweeter flavour than the purple-red variety and can be found at most greengrocers. When trimming the beetroots, leave a little of the stalk intact to prevent bleeding during cooking.