It's basically a fried then grilled pizza sandwich. Or a recomposed pizza. Or a grilled cheese with tomato sauce and pepperoni. Or just a pizza grilled cheese sandwich. Whatever, it takes max 30 minutes and it's bloody delicious.
Crush the tomatoes (you can use a pair of scissors in the can for this). Pour into a medium saucepan.
Add the onion, garlic and olive oil and simmer gently until reduced in volume by half. The sauce should be really thick. Season to taste.
Separate into batches and freeze the ones you aren't using.
Butter both sides of two slices of your bread. Assemble the sandwiches - tomato sauce, pepperoni, sliced mozzarella.
Fry in mild olive oil until toasted with oozing cheese.
Spread more tomato sauce and top with salami and mozzarella and bake until the cheese is bubbling.
Enjoy!