Salt and pepper the trout inside and out and rub in the lemon juice. Place in a greased baking dish and bake in the oven for about 15 minutes.
In the meantime, peel and finely chop the onion, garlic and ginger. In a small bowl, mix the diced onion with the garlic, ginger, tomato paste and the crumbled chilli pepper. Add the whole cherry tomatoes.
Heat the oil in a pan and fry the mixture in it. Pour in the coconut milk and simmer for 5 minutes while stirring.
Spread the mixture on the fish and cook in the oven for another 12 minutes.
This goes well with salad and bread or basmati rice.