Peel potatoes, quarter and boil in salted water for about 15 minutes.
Cook lasagna noodles in plenty of boiling salted water until al dente, then drain.
Beat butter until fluffy. Combine butter, crushed tomatoes and basil. Season with salt and pepper.
Rinse monkfish fillets, pat dry and cut into four equal pieces. Season with salt and pepper.
Rinse and slice tomatoes and zucchini. Add to a steamer with the potatoes and top with monkfish. Season with salt and pepper. Steam fo 8 minutes.
Add lasagne sheets to steamer when 1 minute of cooking time remains.
Mash potatoes with butter and cream, season with salt and pepper.
Layer zucchini, tomatoes, lasagna noodles, monkfish and mashed potatoes in two towers on plates. Drizzle with tomato butter and serve.