Preheat the oven to 180°C.

Mince the onion and soak it in water to remove bitterness, then drain.

Mix all Tuna Mayo ingredients in a bowl until well combined.

Heat water in a microwave-safe container for 20 seconds at 600W.

Combine all dough ingredients in a bowl and mix until no dry flour remains. Knead until smooth.

Cover the dough with plastic wrap and let it rise at room temperature for 20–30 minutes until it doubles in size.

Punch down the dough to release air, divide into 6 portions, and shape into balls.

Place the dough balls on a baking sheet lined with parchment paper. Cover with plastic wrap and a damp cloth, then let rest for 20 minutes.

Cut a cross on the top of each dough ball, add Tuna Mayo, brush with beaten egg, and bake at 180°C for 15 minutes.