Folded around jam, the piadina stops being a savoury wrapper and becomes a warm breakfast pastry, which is the whole shift here. There is no salt, no cured fat, no cheese to balance; instead the soft, faintly fatty Romagnolo round meets nothing but fruit and sugar, and the contrast is heat against sweetness rather than bread against salume. The defining fact is that warmth does the same loosening it does for cured meat, only the effect is different: the residual griddle heat slackens the marmellata so it spreads thin and seeps a little into the crumb, and the plain, lightly savoury dough keeps the jam from reading as cloying the way it would on sweet bread. The flatbread's near-neutrality is exactly what makes the fruit taste of fruit.
Doing it well is about the bread and the temperature, since the filling is one ingredient. The dough is the usual Romagnolo build, flour with lard or oil and barely any leavening, rolled thin and cooked dry on a hot plate until it freckles and stays soft, lifted before it crisps so it folds without snapping. The marmellata, often apricot, fig, or sour cherry, is spread in a thin even layer onto the warm surface rather than dolloped, so it does not pool and burst out at the first bite, and the residual heat thins it just enough to grip the crumb. It is folded in half, sometimes folded again into quarters for a child's hand, and eaten warm while the jam is still slack and the bread still soft. Cold, it sets and the appeal flattens.
The close cousins are a single swap and stay in the same sweet register. There is the chocolate-hazelnut version with Nutella in place of jam, the one spread with honey for a thinner, floral sweetness, and the plainest fold dressed only with sugar melting into the warm round. Each is the same warm flatbread meeting a single changed sweet element, and each deserves its own article rather than being crowded in here.