Place the lentils in a large saucepan with the turmeric, chillies, ginger and measurement water. Bring to the boil, then reduce the heat and simmer, uncovered, for 40 minutes or until the lentils have broken down and the mixture has thickened.
Add the tomatoes and cook for a further 10 minutes or until thickened. Stir in the spinach and cook for 2–3 minutes until wilted.
Prepare the spiced oil. Heat the oil in a small frying pan, add the shallot and cook over a medium-high heat, stirring, for 2–3 minutes until golden brown. Add all the remaining ingredients and cook, stirring constantly, for 1–2 minutes until the seeds start to pop.
Tip the spiced oil into the dhal, stir well and season to taste with salt. Serve with naan bread or steamed basmati rice, if liked.