Preheat 2-sided tabletop grill. Cut four 1/2-inch thick slices from ham (reserve any remaining ham for another use). Place butter, brown sugar and rum extract in small microwave-safe bowl. Microwave on HIGH 30–45 seconds or until butter melts.
Brush one side of ham with glaze and place on grill with glazed side down. Brush glaze on top of ham slices. Close grill lid, pressing down firmly to sear ham. Grill 4–5 minutes, brushing once with remaining glaze, until internal temperature reaches 140°F Remove ham from grill and cover to keep warm.
Cut pineapple into four 1/2- to 1-inch thick slices and place on grill; close lid. Grill 1–2 minutes until warm. Serve with ham.