To make the dough, place all of the ingredients into the Thermomix bowl and knead for 3 minutes. Transfer to a warmed bowl, cover and allow to rise till double in size for approximately an hour. When ready, knock out the air from the dough and line grease a rectangular baking tray with a little oil. Press in the dough and drizzle over the remaining 2 tbsp olive oil. Cover the top with the sliced onions, tuna, olives, capers and sun-dried tomatoes (and anchovies if using) Allow to rise again till double in size before baking in the oven at 220`c for approximately 25 minutes. Serve cut into squares.