Peel and core pineapple. Cut crosswise into 1/2-inch slices.
Spray cold cooking grate with cooking spray, and place on grill, over medium-high heat (350º to 400º). Place pineapple slices on cooking grate, and grill 2 to 3 minutes on each side or until grill marks appear.
Melt 4 Tbsp. butter in a large skillet over medium heat. Stir in brown sugar, and cook until sugar dissolves. Add grilled pineapple, spooning sugar mixture over pineapple, and cook 3 minutes or until mixture is thickened and pineapple is glazed. Top pineapple with ice cream; sprinkle evenly with coconut and macadamia nuts.