For the gratinated tuna baguettes, cut the baguette in half crosswise. Drain tuna, slice mozzarella and slice onion into rings. Spread herb cream cheese on the baguette halves.
Top with onion rings, tuna and mozzarella slices. Sprinkle with oregano and basil and bake in the oven at 180 °C for about 8 minutes.
Arrange the tuna baguettes and serve.