Preheat the grill to high. Place the peppers on a baking sheet and cook under the preheated
grill, turning frequently, for 10 minutes or until the skin is blackened and blistered all over.
Using tongs, transfer to a plastic bag, then tie the top and cool.
Meanwhile, whisk the olive oil, lemon juice, vinegar, garlic, paprika, chilli flakes and sugar
together in a small bowl.
When the peppers are cool enough to handle, peel off the skins, then cut the flesh into thirds
lengthways and deseed. Place the pepper pieces in a non-metallic dish and pour over the dressing,
turning to coat. Stand in a cool place for 30 minutes.
Rub the salt off the capers and mix with the tuna. Drain the pepper pieces, reserving the
dressing. Divide the tuna mixture between the pepper pieces and roll up. Secure with a wooden
cocktail stick. Place the tuna rolls on a serving platter, then spoon over the dressing and serve
at room temperature.