Preheat oven to 400 - 425 degrees F (200 -220 degrees C). Grease a large, 12x18-inch rimmed baking sheet with 1 tablespoon butter.
Combine 14 tablespoons butter and sugar in a large bowl; beat with an electric mixer until smooth and creamy.
Mix flour, baking powder, lemon zest, and salt in a bowl. Alternate adding flour mixture and eggs to the creamed butter mixture. Spread batter onto the prepared baking sheet; dough is very sticky, so use a spatula to spread it onto the tray. Distribute sliced apples evenly on top and drizzle with lemon juice. Sprinkle with raisins.
Bake in the preheated oven until set and lightly browned, about 30 minutes.