Preheat oven to 350 degrees. In a large stand mixer, combine cake mix, eggs, oil, sour cream, water and instant pudding mix.
Grease two 8 or 9 inch round cake pans. (She suggests 8 in. but I used 9 and it turned out fine. If you have 8 in. pans it would probably make the topping thicker) Layer bottom of both pans with sliced bananas.
In a small saucepan, melt butter and add brown sugar and lemon juice. Stir until completely melted and combined. Pour sauce over bananas. Top each pan with 1 cup of the shredded coconut.
Divide cake batter in half and pour into each pan. Spread evenly. Bake at 350 degrees for 35-40 minutes. Let rest 5-10 minutes and invert on serving plate. As I said above, many of the bananas might stay in the pan simply pull them out and arrange on cake.