They call it "invisible" because it'll disappear pretty much as soon as you serve it.
6 apples, peeled and halved
Juice of 1 lemon
3 large eggs
1/4 cup sugar
2 tablespoons butter, melted
1 cup all-purpose flour, plus 1 tablespoon for dusting
1 teaspoon baking powder
1 teaspoon cinnamon
1 teaspoon salt
1/2 cup whole milk
1 teaspoon vanilla
1 1/2 cups raspberries, divided
2 tablespoons powdered sugar
1/4 cup slivered almonds
Prepare the apples: Using a mandolin on the smallest setting, slice apples into pieces approximately 1/8-inch thick. Place in a bowl and cover with lemon juice. Set aside while you make the batter.
Make the cake: Preheat the oven to 350 degrees, and prepare a 9 by 5-inch loaf pan with baking spray and flour.
In a large bowl, whisk eggs and sugar until frothy. Add butter and stir. Add flour, baking powder, salt, and cinnamon. Stir in milk and vanilla and mix until smooth. Cake mix will resemble pancake batter. Pour over prepared apples and make sure all pieces are covered and still intact. Carefully stack apples layer by layer, creating the invisible layers. Fill the pan two-thirds high, then top with a layer of one cup of raspberries all standing up in a row. Cover with the remaining apples and bake for 45 to 50 minutes. Allow to cool for 30 minutes, and then flip out onto a cooling rack and cool for another 30 minutes before serving. Dust with powdered sugar and top with slivered almonds and raspberries. Cake will keep up to 4 days covered.