Make your crumb topping. Mix together the brown sugar, flour, granulated sugar and cinnamon, then cut in your cold butter until you have chunky crumbs. Place it in the fridge while you make the cake.
Cream together your butter and sugar. Toss in your egg and vanilla, then fold in your sour cream until everything is just mixed.
Measure out your flour, baking powder, baking soda and salt and set aside.
Peel and slice 3 cups of apples into ¼ inch slices. Toss them with the lemon juice.
Add half of your flour mixture to your wet mixture and slowly let it mix.
Add the rest of your flour mixture and half of your apples, then mix again gently. Add the rest of your apples and let everything cover itself just a little bit.
Pour the batter into a buttered springform pan and top with your chilled crumb mixture.
Bake at 350°F. Start with 1 hour, then specifically check the center to make sure it’s done. Depending on your pan and oven, it may need a little longer.
