Heat oven to 350F. In a 12 cup Bundt pan, pour melted butter , cover butter evenly with the brown sugar. Place the pineapple slices over the brown sugar, placing them evenly in bottom of bundt pan . Place cherry in the pineapple hole.
In a large bowl, beat cake mix, pineapple juice, coconut extract, oil & eggs with electric mixer on low speed until moistened; beat 2 minutes on high speed. Fold in walnuts. Pour into pan over fruit.
Bake 40 to 45 minutes or until cake is golden brown and springs back when touch lightly. Cool cake for 10 to 15 minutes. Place plate over cooled cake; turn plate and pan over. Remove pan.