Cut the tops off the tomatoes and scoop out the cores with a spoon. Don't throw them away, they'll be useful for the filling.
Chop the parsley and mince the garlic.
Finely chop the onion.
Finely chop the tomato cores and fry them with onion and garlic in vegetable oil for 5 minutes. Add salt and pepper.
Mix the filling with chopped parsley and stuff the tomatoes with it.
Sprinkle the top of the filling with breadcrumbs and add a teaspoon of butter to each tomato.
Place the tomatoes in a baking dish lined with parchment paper and cover with the tops. Bake the tomatoes in the oven for 10-15 minutes.
Place the tomatoes on fresh lettuce leaves and sprinkle with chopped parsley. Garnish the plate with freshly ground black pepper.