Cut away the top and base of the pineapple, then cut down the sides, removing all the dark ‘eyes’. Cut the pineapple into thin slices. Using an apple corer, remove the hard, central core from each slice.
Melt the butter in a frying pan with the sugar. Add the orange juice and stir until hot. Add as many pineapple slices as the pan will hold, and cook for 1–2 minutes, turning once. As each pineapple slice browns, remove to a plate.
Return all the pineapple slices to the pan, heat briefly, then pour over the vodka and carefully light with a long match. Let the flames die down, then sprinkle with the almonds and serve at once.