Add the lemon zest, half a teaspoon of cumin, if you are using it, and the spinach. Cover the pan and leave it alone for about three minutes. When the spinach has wilted down add the rice, vegetable stock (or water) and most of the dill. Season with salt and pepper and give it a stir. Bring the pot to a boil and then turn it down to a simmer, give it another stir and put the lid back on, after about 15 or 20 minutes the rice will be cooked. You can look in on it if you are concerned and give it a stir if you think it might be sticking to the pan. When the rice is cooked, stir in the remaining dill and the juice of the lemon and leave it off the heat, covered, to allow the flavours to mingle for a few minutes and it is ready to serve.
I had mine with a fillet of cod that was on sale, which I marinated in olive oil, with a little garlic, lemon juice, dill, salt, pepper and then roasted in a 200℃ oven in a half open parcel of tin foil for 20 minutes.