Mix water, yeast and sugar in the bowl of an electric mixer and set aside for 5 minutes or until foamy.
Using the dough hook, turn on medium-low speed and mix the yeast mixture with flour and butter for 2 minutes.
Add salt and mix for a further 8 minutes or until smooth. Transfer dough to a slightly greased mixing bowl and place in the steam oven to ‘steam function’, set at 30°C for 45 minutes.
Grease a 23cm bundt pan. Turn dough out onto a lightly floured surface| and pinch off 80g of dough; reserve.
Gently knock back the remaining dough and press into a rectangle. Scatter with cheese, prosciutto and salami, and roll into a log around 30cm long, ensuring the ingredients are enclosed fully.
Place dough into the prepared pan, joining and pinching the ends to make a complete circle. Place tomatoes, diagonally across from each other to form a cross pattern.
Roll the reserved dough into 8 small logs and cross 2 pieces, overlapping, to make a cross on top of each tomato. Return to the steam oven, set at 30°C and prove for 45 minutes.
Preheat the oven on fan forced, set at 180°C, with low steam. Place in the oven and cook for 35 minutes until golden brown; set aside to cool slightly. Turn out onto a cooling rack. Serve warm or at room temperature.