Clean the snails and boil them for about 15 minutes in salted water, adding the vinegar at the very end. Then drain and remove the meat from the shells.
Separately, fry the cut into crescents onions in a little oil and water. Add the carrot and celery, finely diced, and the pepper, cut into coarse pieces. Let them soften slightly and add the flour, diluted in tomato paste and a little water. Stir and pour in the white wine.
Once it's boiling, add the bay leaf, black pepper and salt to taste. Add the snails, stir and simmer for 5 minutes. Then transfer everything into a lightly greased tray.
Sprinkle with lemon juice and put it to bake for about 20-25 minutes.