Melt butter in a medium, heavy-bottomed saucepan. Add the rice, lemon zest, vanilla seeds and scraped vanilla bean. Cook, stirring constantly for a few minutes. Add the milk all at once and cook over low flame, stirring constantly. It will take about 30 minutes for the rice to absorb all the liquid.

When the rice is soft and all the liquid is absorbed, remove vanilla pod and add sugar, mixing well.

Pour into a shallow pan, cover with plastic wrap, and refrigerate until cool. When cold, fold in the whipped cream. Serve with fresh or dried fruits.