1Heat oven to 350°F (325°F for dark or nonstick pans). Grease and lightly flour bottoms and sides of two 8- or 9-inch round cake pans or bottom only of 13x9-inch pan.
2In large bowl, beat cake mix, pineapple, water, oil, eggs and 1 teaspoon of the rum extract with electric mixer on low speed 2 minutes, scraping bowl occasionally (do not overbeat). Pour into pan(s).
3Bake as directed on box. For rounds, cool 10 minutes. Run knife around sides of pans to loosen cakes; remove from pans to cooling rack. Cool completely, about 1 hour. Cool 13x9 in pan.
4Stir remaining 1 teaspoon rum extract into frosting. Place 1 cake layer, rounded side down, on serving plate. Spread with 1/3 cup frosting. Top with second layer, rounded side up. Frost side and top of cake with remaining frosting; sprinkle with toasted coconut. For 13x9, frost top of cake with frosting; sprinkle with toasted coconut. Store loosely covered.