Preheat the oven to 375 degrees F. Place the sweet potatoes in a 2-quart baking dish. Set aside.
In a medium pot, melt the butter over medium-low heat. Add the sugar and stir until smooth. Drain the pineapple in a strainer, reserving the juice. Stir in about half the pineapple and half the pineapple juice; reserve the rest of the pineapple and juice for another use. Stir in the cinnamon, cloves and salt. Bring the mixture to a boil, remove from the heat and add the vanilla extract. Pour the mixture directly over the sweet potatoes.
Cover the dish with aluminum foil and bake until the sweet potatoes are just tender, about 45 minutes. Remove the foil and continue to bake until the sweet potatoes are caramelized, 20 to 25 minutes more.
Plate and serve immediately. Pour extra sauce from the bottom of the baking dish on top.