Step 1Combine brown sugar, orange and lime juices, cinnamon and vanilla bean in small saucepan over medium-low heat. Cook, stirring, until sauce boils. Continue cooking until sugar dissolves and sauce is clear. Discard vanilla bean. (Can be made 2 days ahead and refrigerated.)
Step 2Place pineapple slices in 9-inch square baking dish, overlapping slightly. Pour 1/2 sauce over pineapple.
Step 3Bake at 450 degrees, basting every 5 minutes, until pineapple is golden and sauce is bubbling, about 15 minutes.
Step 4To serve, place 1 scoop ice cream in each of 6 bowls. Divide pineapple slices among bowls. Spoon 2 tablespoons warm sauce over top. Serve immediately, passing remaining warm sauce.