Preheat oven to 350 degrees Fahrenheit. Spray an Bundt Pan with cooking spray.
Sprinkle plantain slices with cinnamon and allspice (optional). Add 1 1/2 tablespoons butter and 1 1/2 tablespoons brown sugar and to a large skillet over medium heat. Add 1/2 of the plantain slices and cook for 3-4 minutes per side, or until golden brown; remove the cooked plantains. Add another 1 1/2 tablespoons butter and 1 1/2 tablespoons brown sugar to the skillet; add the remaining plantain slices to the pan and cook for 3-4 minutes per side, or until golden brown. Remove the cooked plantains. Once cool, cut each of the cooked plantain slices into 3 pieces.
In a large bowl fitted with an electric mixer, cream 1 cup butter, 1 1/2 cups brown sugar, and granulated sugar until light and frothy. Add 1/2 cup of the ginger beer. Add the eggs one at a time, beating well after the addition of each egg.
In a medium mixing bowl, sift together the flour, baking powder, baking soda, ground ginger, and salt.
With the mixer on low speed, alternately add the dry ingredients and 1/2 cup of the ginger beer; add grated ginger, lemon juice, and vanilla extract, mixing well.
Pour about 1/2 of the batter into the sprayed pan. Layer 1/2 of the plantains over the batter. Top with the remaining 1/2 of the batter and layer the remaining 1/2 of the plantains on top. Bake 45-55 minutes or until toothpick inserted into the center of the cake comes out clean.
Remove from the oven and let the cake cool in the pan for 10 minutes. Turn out cake onto platter. Cool.
In a small bowl, combine confectioners sugar and 3 tablespoons ginger beer. Mix until well-combined (if necessary, add more sugar or ginger beer to get desired consistency). Drizzle glaze on cake with spoon. Sprinkle 3/4 toasted coconut on top of cake. After cutting the cake, sprinkle the remaining 1/2 cup toasted coconut on the individual serving plates and/or on top of the individual slices of cake.