Preheat the oven to three hundred and fifty degrees, and grease a large baking pan.
On the stovetop, melt together one-half cup of butter and brown sugar. Add three-quarter cups of unsweetened coconut and mix well.
In a separate bowl, blend three and one-half cups of Bisquick, one-half teaspoon of baking powder, and one-quarter tea spoon of salt.
Whip three egg whites in another bowl with a mixer until stiff peaks form.
Beat one cup of sugar and the three-quarter cups of butter in a bowl with a mixer. Add another cup of sugar, one cup of buttermilk, pineapple juice, three egg yolks, and one teaspoon of vanilla. Add the Bisquick mixture and mix until well combined. Gently fold in the egg whites.
Place the butter/brown sugar mixture into the greased pan and arrange the pineapple chunks on top. Pour the batter over the top of the pineapple, and bake until done, and the top is brown. Let cool for half an hour. Flip the cake over. Serve and enjoy.