Heat the vegetable oil in a large saucepan over medium heat. Add the chopped onion and sauté for 5 minutes until soft and golden.
Add the garlic, ginger, and fenugreek seeds. Fry for 1 minute until fragrant.
Stir in the cumin, coriander, turmeric, chilli powder, and sugar. Cook for another minute.
Add the red lentils, chopped tomato, carrot, aubergine, and potato. Mix well to coat everything in the spices.
Pour in the water and bring to a boil. Reduce heat, cover, and simmer for 20 minutes until the vegetables and lentils are soft.
Use a hand blender to lightly blend the mixture in the pot until thick and creamy but with some texture remaining.
Add the prawns and simmer for 5–6 minutes until they are pink and cooked through.
Stir in the garam masala and lemon juice. Adjust salt to taste.
Garnish with fresh coriander before serving.
