Clean and wash the spinach. Peel the onions and finely dice them.
Heat the oil in a saucepan and sweat half of the onions in it until translucent, then add the spinach. Season with salt and pepper.
Clean, wash and finely chop the pepper. Melt the butter in a saucepan. Sweat the peppers and the remaining onions in it. Pour in the broth, bring to the boil and simmer for about 5 minutes. Pour in the cream. Salt, pepper and puree.
Cut the fish fillet into 8 pieces, season with salt and pepper. Pour the pepper sauce into a large or 2 small casserole dish and put the fish in it. Spread the spinach on top.
Grate the cheese and sprinkle over it. Cook at 200 ° C for about 15 minutes.