Add the tomato paste and stir for another 2-3 min. Add the diced tomatoes, broth and water. Stir and lower the heat.
To make the rusks, cut the baguette into slices, smear each one of them with olive oil. Put the parmesan in a nonstick frying pan, into several piles.
Put a piece of baguette on top of each pile. Press down with a spatula, so that the cheese sticks to the bread. Repeat this procedure on the other side of the baguette pieces.
Serve the soup with thus prepared rusks and a little basil.