Preheat oven to 350°F (175°C) and grease a baking pan.
In a bowl, whisk flour, baking powder, baking soda, salt, and cinnamon.
In another bowl, cream butter and sugars until light and fluffy.
Add eggs one at a time, then mix in vanilla.
Add dry ingredients alternately with milk, mixing gently until just combined.
Pour half the batter into the pan.
Sprinkle half the cinnamon sugar and apples over the batter.
Add remaining batter, then top with remaining apples and cinnamon sugar.
Swirl lightly with a knife for a layered look.
Bake until golden and a toothpick comes out with a few moist crumbs.
Cool slightly, then drizzle with glaze if using.