Grease and flour an 8" round springform pan. Set aside.
Preheat oven to 375 degrees F.
to make the topping:
In a medium bowl, whisk together both sugars, cinnamon, salt and flour. Add melted butter and fluff with fork until mixtures creates crumbs. Set aside.
to make the cake:
In a medium mixing bowl, whisk together flour, sugar, baking powder, cinnamon, baking soda and salt. In a large measuring cup, mix together milk, vanilla, oil and egg. Whisk until smooth.
Add the wet ingredients to the dry ingredients and stir with a wooden spoon. Do not over mix. Few lumps in the batter are okay.
Pour the cake batter into the prepared pan.
In a medium bowl, toss together apple slices with two tablespoons of sugar, ½ teaspoon of cinnamon and the apple cider vinegar. Set aside.
Arrange apple slices over the batter.
Sprinkle crumb topping over the apples covering completely.
Bake the cake for 30 to 35 minutes or until the topping is golden brown.
Let cool completely in the pan.
Transfer onto a serving plate or stand. Slice and serve.
Keep in a covered container for up to 4 days.
Notes
I highly recommend drizzling caramel sauce over each slice just before serving. It makes it that much more amazing. Try my Microwave Caramel Sauce - it's the easiest and the best caramel sauce ever! You can make it while the cake cools! You can also top it with a scoop of delicious sweet vanilla ice cream.