Cut the onion in half, then slice thinly.
Grind roughly the fennel seeds in a mortar.
Rub the new potatoes, cut in half if they are bigger than bite size.
Heat the oil in a heavy based saucepan, then soften the onion, garlic and fennel seeds for about 5 minutes while constantly stirring. Add the paprika, stir for one minute.
Add the potatoes, stir for a minute, then pour in the stock and the tinned tomatoes. Bring to the boil, then simmer for 10 minutes at low-temperature.
Meanwhile, grate the lemon zest, then cut the lemon into wedges. Chop up the parsley.
When the potatoes are tender, but not completely cooked through, add the frozen fish, cover and cook for 10 minutes.
Season with salt and pepper, then stir in most of the lemon zest and parsley. Gently stir through - the fish falls apart a bit.
Serve with lemon wedge, scattered with the remaining parsley.