Put the flour, ½ tsp sugar, salt and yeast into a large bowl or free standing mixer.
Add 1 tablespoon of olive oil and 300ml of warm water.
Knead for 5-10 minutes, until smooth.
Cover and leave to rise in a warm place for 30 minutes and doubled in size.
Preheat the oven to 220°C / 425°F / Gas mark 7.
Line 2 baking trays with greaseproof paper and brush will oil.
Heat 1 tablespoon of oil, add the onions and fry gently for 10 minutes until softened.
Stir in the garlic and cook for 2 minutes, stirring.
Add the tomatoes, herbs and the rest of the sugar.
Simmer for 10 minutes then remove from the heat to cool.
Cut the pizza dough in half.
Lightly knead until smooth and roll out to 3mm thick.
Use an 18cm plate to stamp out 3 dough rounds.
Repeat with the rest of the dough so there are 6 total.
Stir the tuna, olives and mozzarella into the tomato mixture and spoon it over the left of centre on each round.
Brush the dough edges with water and fold it over the filling, crimping the edges together firmly.
Pierce 2 holes in the tops of each with a knife.
Place on the baking tray and bake for 20 minutes and the bases are firm.
Allow to cool before serving with a little thyme if using.