Add all of the ingredients, except the optional extra 500ml water, to your slow cooker and cook on medium for around 4 hours (or according to your slow cooker instructions). If you would like to reduce the liquid, leave it to cook for an hour longer with the lid off.Note: This makes quite a spicy soup, so if you prefer mildly spicy dishes start with 1/4 tsp of chilli flakes. You can always add more at the end. 200 g red lentils, 100 g onion, 50 g dried apricots, 1 tbsp lemon juice, 1/2 tsp celery salt, 1/2 tsp fenugreek, 1/2 tsp turmeric, 1/2 tsp dried chilli flakes, 1 tsp cumin seeds, 1/4 tsp fennel seeds, 1 litre vegetable stock