Rinse the red lentils until the water runs clear, then simmer with the water and turmeric for 20-25 minutes until collapsed and thick. Skim any foam in the first few minutes.

Meanwhile soften the diced onion in oil for 8 minutes, then add half the garlic and all the ginger for 1 minute.

Add the tomatoes and cook down for 5 minutes, then stir this into the lentils with the salt.

For the tarka: melt the butter in a small pan until foaming, add the cumin seeds and remaining sliced garlic, and fry for 30-45 seconds until the garlic is golden — not brown.

Kill the heat, add the chili flakes to the residual warmth, and pour the whole thing over the dal.

Stir through once, leaving streaks. Serve with rice or flatbread.