Defrost the prawns if necessary. Wash the tomatoes and cut them into pieces. Clean and wash spring onions and cut them into rings. Peel onion and grate it coarsely on a kitchen grater. Chop peanuts roughly.
Carve the prawns lengthwise on the back and remove the dark intestine with a sharp knife. Rinse shrimps and dab dry.
Heat the oil in a large frying pan. Fry the prawns for 2-3 minutes while turning. Season with salt and pepper and remove. Sauté the onion in the frying fat. Add tomatoes and braise briefly. Melt peanut butter while stirring.
Add 300 ml water and bring to the boil.
Put rice noodles in a bowl and pour boiling water over them. Let it swell for about 3 minutes.
Add the prawns and spring onions to the sauce and heat briefly. Season to taste with soy sauce and cayenne pepper. Drain the noodles. Serve with the prawns in the peanut sauce. Serve sprinkled with fried onions and peanuts.