Grease a 12-inch round baking pan with butter and cover the bottom with 5 ounces of muscovado sugar. Arrange the 8 slices of pineapple at the bottom of the baking pan with a cherry in the center of each slice. Separately, mix 1½ cups of butter, ¾ cup sugar, 3 eggs, the condensed milk, 3 cups sifted flour, 1 teaspoon baking powder, and 1 cup pineapple syrup. Pour the batter into the pan and bake at 390 degrees for 25 minutes. Let it cool and turn pan upside down over serving plate. Remove pan carefully.