Preheat the oven to 200C/400F/Gas 6.
Place the tuna, cherry tomatoes, parsley and jalapeno peppers into a bowl and mix well.
Spoon the tuna mixture onto the baguette then sprinkle over with grated cheddar and salt and freshly ground black pepper, to taste.
Place onto a baking sheet then into the oven to bake for 5-6 minutes, or until the cheese has melted.
To serve, slice in half and place on a warm plate.