Put the flours into a large bowl or the bowl of a stand mixer

Add the salt and yeast into the bowl, making the two don’t come into direct contact. Stir to combine

Add the oil and gradually pour in the water – you may not need it all – until you have a soft dough. If using a stand mixer, knead with a dough hook attachment for 5 minutes. Otherwise, lightly dust your surface, tip the dough out, and knead for 10 minutes until soft and springy

Cover the dough and leave to prove for 1 hour until doubled in size

While the dough proves, put the onions into a large frying pan with the oil and fry for 15–20 minutes, stirring occasionally until softened and starting to brown

Add in the sugar and fry for 2–3 minutes until caramelised. Transfer the onions to a bowl to cool completely

Once cool, add in the mozzarella and tomatoes and mix to combine

Lightly dust the work surface with flour and roll out the dough to 20 × 50 cm. Cover the dough evenly with the onion filling

Roll up the dough tightly from the shorter side, making sure to finish with the seam at the bottom

Slice the log into six pieces

Grease and line the base of a deep, spring-bottom 20 cm cake tin with oil and baking paper

Place the rolls into the tin, evenly spaced apart, and cover. Leave to prove for 30 minutes until risen slightly

Meanwhile, preheat the oven to 220°C (200°C fan) and bake for 25–30 minutes until golden

These can be served warm, after being left to cool in the tin for just 20 minutes, or allowed to cool completely in the tin. If you prefer a softer crust, cover the tins with a tea towel to steam them slightly while they cool