Wash, clean and dice the tomatoes, season them in a large pot with salt, pepper and a little sugar, mix them and let them rest for about 10 minutes to draw some water
Peel, wash and halve the potatoes and cook in boiling salted water for about 20 minutes. Bring the tomatoes to the boil, cover and simmer for about 15 minutes, adding a little water in between if necessary
Clean, wash and chop the spring onions. Fish wash, dab dry, cut into pieces, season with salt and pepper. Wash basil, shake dry. Pluck the leaves from the stems and chop them, except for a little bit for garnishing
Add basil, spring onions, 100 ml water and tomato paste to the tomatoes, stir in, season again. Place the fish pieces on top and steam covered for 6-8 minutes. Drain the potatoes, if necessary season with some pepper. Arrange fish, sauce and potatoes, garnish with basil