Cut the zucchini lengthwise and hollow out most of the flesh.
Drizzle with olive oil and bake until lightly brown.
In the meantime, chop the zucchini flesh and fry it in some olive oil together with the chopped onion and tomatoes.
Season to taste and remove from the heat.
Fill the zucchini with the mixture and place a hot dog on top.
Grate some mozzarella or cheddar on top of the hotdogs and cook until the hotdogs are piping hot.
Drizzle some mustard and serve with French fries or crisps.