Fresh sardines on toast with sweet pickled red onion Recipe

4 whole sardines, cleaned, heads removed
1 tbsp plain flour
flaked sea salt
freshly ground black pepper
3 tbsp olive oil
1 red onion, sliced
1 tbsp caster sugar
2 tbsp red wine vinegar
1 tbsp small capers, drained
1 heaped tbsp chopped fresh parsley
4 slices sourdough bread
50g/1Âžoz butter, softened
2 tsp wholegrain mustard
1 ripe tomato, finely sliced

Using a sharp knife, cut the sardines from the opening in the underside (where it has been cleaned) to the beginning of the tail, so the fish can be butterflied open. Trim off the tail and fins with scissors.
Open the fish flat onto a board, skin side up. Carefully push the backbone of the sardine down onto the board with your fingertips all the way along the length of the fish until it flattens out. This will loosen the spine from the fish but if you press too hard, you will turn the sardine flesh to mush.
Flip the fish onto its back and gently ease your finger underneath the spine, lifting it away from the flesh, taking out the little bones as you go. Use the point of a sharp knife to tease any bones away from the flesh if necessary. Run your hands up and down the flesh to check for any little bones. Set aside while you repeat the process with the other fish.
Place the flour onto a plate and season with a pinch of salt and plenty of freshly ground black pepper. Coat each sardine in the seasoned flour, shaking off any excess flour as you go. Set aside until the pickled onion is almost ready
For the sweet pickled onion, heat one tablespoon of the oil in a medium non-stick saucepan. Add the sliced onion and cook over a medium heat for 4-5 minutes, stirring regularly until softened but not coloured. Stir in the sugar, vinegar, capers and cook for a few seconds more, stirring constantly. Remove from the heat and stir in the parsley.
Heat the remaining oil in a large non-stick frying pan set over a medium high heat. Fry the sardines for a minute on each side.
To serve, toast the sourdough bread. Mix the softened butter with the mustard and slather over the hot toast. Top each piece of toast with a few slices of tomato, a sardine and the warm onion pickle.