Rice verde one-pot
Preheat the oven to 180°C/ 350°F/Gas mark 4.
Melt the butter in a large casserole dish and sauté the onion until it is transparent. Stir in the rice, spinach, milk, egg, salt and cheese. Mix well with a fork.
Cover and bake for about 30 minutes, until the mixture is hot and the top is crisp.