Soak the yellow dried split peas overnight.
The next day rinse and drain them, then put them in a pan and add one litre of water. Add the tomatoes, turmeric, chilli and ginger. Bring to the boil, then gently simmer for about 1 hour, until tender and there is little liquid around the peas.
Heat the oil in a frying pan. Add the garlic, curry leaves and cumin. Season with salt and pepper. Cook for a couple of minutes, stirring, then add the spinach.
When the spinach has almost wilted, take the pan off the heat and pour the mixture over the dal. Combine well and rest for a minute. Season to taste.
Scatter some chopped coriander on top just before serving.