Preheat the oven: preheat the oven to 180°C / 350-375°F / Gas Mark 4-5.
Saute spinach: place a large frying pan onto the stove top, turn the heat to high. Add the butter and let it melt. Then add the garlic, salt and pepper and cook for 1 minute. Add the spinach leaves and cayenne pepper. Let the spinach wilt, stirring for 1 - 2 minutes.
Spinach and cheese: add the ricotta cheese, cheddar cheese, parmesan cheese and pecorino romano to a mixing bowl. Then add the cooked spinach and stir to combine. Set aside for now.
Polenta: without rinsing or cleaning the pan that you used to cook the spinach, place it back on the stove with the heat on high and add the dried polenta, salt and room temperature water. Then pour in the boiling water. Cook until the polenta comes away from the insides of the pan.
Baking dish: spray a large baking dish with cooking spray. Then portion half of the cooked polenta into the bottom of the dish and use a wooden spoon to portion into one flat layer. Pile the spinach and ricotta cheese mixture on top of the polenta and spread to form its own layer. Then spread the remaining polenta on top of the spinach layer. Sprinkle reserved cheddar, parmesan cheese and pecorino romano on top.
Oven bake: place the baking dish into the oven on the middle shelf. Allow it to bake for 20 - 25 minutes until golden brown. Once cooked use oven mits to remove the baking dish from the oven and place it onto a heatproof surface.
Garnish: sprinkle black pepper and finely chopped parsley over the top of the dish and serve immediately.