Quarter the tomatoes and remove the seeds. Put the tomatoes in the XL steaming bowl and mix in the onion and garlic.
Remove the bottom from steam bowl 3. Place steaming bowl 3 onsteaming bowl 2, and place both on the drip tray. Hang the XL steaming bowl in steaming bowl 3.
Pour the stock over the tomatoes and stir in 1 tablespoon olive oil.Put the lid on the steaming bowl. Set the timer to 30 minutes and steam until the tomatoes are tender.
In the meantime pre-heat the oven to 200 °C. Divide the ciabatta cubes over a baking tin and sprinkle them with 2 tablespoons olive oil and the sea salt. Bake the croutons for 10 minutes in the oven until golden brown.
Purée the tomatoes with the stock in the blender and season to taste.
Serve the tomato soup in bowls and garnish with croutons, Parmesan cheeseand basil.