You will need a couple slices of bread [whatever you have is fine], tomatoes, salt, pepper, herbs, garlic, and parmesan cheese. Rather than roasting over coals, I get my cast iron up to a medium heat and toss in some olive oil and a little butter [don't judge]. Then you'll cook the bread on both sides and take it out of the pan. Rub it with a garlic clove if you like that sort of thing.
Next throw in some halved graped tomatoes with oregano, basil, or whatever you like, and a crack of sea salt.
At this point the pan is so hot that you don't have to cook them very long, just until they start to burst. Then top the bread with these, add some pepper, and grate some parmesan cheese on top.