Preheat the oven to 350 degrees. Generously grease a 9-inch springform pan (or 9-inch square pan) with butter or spray with cooking spray. Set aside for now.
Cream the sugar and butter in a large mixing bowl until light and fluffy. Beat in the eggs one at a time. Stir in the vanilla. Add the flour and sour cream alternately beating well after each addition. Spread the batter in the prepared pan.
Core the apple and slice it into ¼ inch thick slices. Put the slices in a bowl and sprinkle them with the lemon juice, brown sugar and cinnamon. Toss apple slices to coat. Arrange the slices around the top of the batter.
To make the topping: Mix together the flour, brown sugar, butter and cinnamon using a pastry cutter, two forks, or a food processor until the mixture resembles coarse crumbs. Stir in the pecan pieces and raisins. Sprinkle topping evenly on top of the layer of apple slices.
Bake for 1 hour, or until a toothpick inserted into the center comes out clean. Start checking for doneness after about 45 minutes. If you feel that the topping is getting too brown, tent the top of the pan with foil to prevent burning.
Remove from the oven and allow to cool in the pan on a rack for 30 minutes. When the cake is cool, remove the side of the springform pan and place on a serving plate.
Optional: Mix the confectioner’s sugar, milk, and vanilla in a small bowl. Drizzle with the icing.
Cut into wedges to serve.
I rarely use the icing on this coffee cake because it's just so delicious without it. But if you really want to "gild the lily," then go for it!