Gently fry the onion and garlic until softened but not browned. Add the tomatoes, rice and thyme to the pan and stir. In another saucepan you should have the chicken stock simmering, stir the turmeric in to the stock and then ladle the stock into the rice. You can put about a third of the stock in at a time. Stir the rice well to make sure it isn’t sticking to the bottom of the pan. You don’t have to be nearly as vigilant with this as you do with risotto so you can leave it to simmer and prep your veg or pull it out of the freezer as the case may be.
Keep adding the stock and giving the rice a stir until it is nearly cooked or you are nearly out of stock. Have a test nibble of a couple of grains of rice to see how it is. When it is nearly done add the prawns and veg and the last of the stock and stir in and simmer for a few minutes until the veg and prawns are warmed through. Take it off the heat and cover. Paella benefits from being left to rest for five or ten minutes so all the flavours mingle, if you have the patience for that, if not, just eat it!