Heat the oil in a large skillet over medium heat. Add the cumin, coriander and cardamom and sauté until they just start to turn light golden, 1–2 minutes.

Add the onions and continue to cook, stirring occasionally, until they turn translucent and start to caramelize, about 5–7 minutes.

Add the ginger, garlic, green chillies, turmeric, powdered chillies and hing and continue to cook for another 2 minutes.

Add the tomatoes, preserved lemons, if using, salt and ½ cup water and cook, stirring frequently, until the tomatoes start to break down, about 2–3 minutes.

Add half the greens and stir to coat in the spiced tomato mixture. Allow the greens to wilt for a couple minutes and then add the remaining greens, stirring again.

Cover and cook until the greens are cooked through and very tender, about 15 minutes.

Turn off the heat and allow to cool for 5 minutes.

Transfer the greens to a food processor and blend until a semi-coarse, but uniform purée forms.

Transfer the blended greens back to the skillet and place back on medium heat until reheated through. If the mixture is a little thick, add a few tablespoons of water at a time until it reaches your desired consistency.

Reduce heat to low and keep warm while you make the tadka.

To make the tadka, heat the ghee in a small skillet or saucepan over medium heat.

Add the cumin seeds and whole chillies and cook, swirling the spices, until the cumin seeds start to pop and sputter, about 1–2 minutes.

Turn off the heat and add the powdered chillies and salt, mixing well.

To serve, transfer the saag to a shallow bowl or serving dish. Pour the tadka over the saag. Enjoy with basmati rice, chapati or makki ki roti.