1/2 c  + 2 Tbls. unsalted butter,
Softened
3/4 c  Sugar
1 ts Cinnamon
1 lg Egg
2 tb Sour cream
1 ts Vanilla
1 c  Flour
1/2 ts Baking powder
1/4 ts Baking soda
1/8 ts Salt
2 lg (or 3 medium) tart apples
(Jonathan, Northern Spy or
Granny Smith) peeled, thinly
Sliced

Put rack in center of oven & heat to 350. Butter 9″ springform pan.
Mix 1/2 cup butter with 1/2 cup sugar, 1/2 tsp. cinnamon, egg, sour
cream & vanilla with mixer or metal blade of food processor until
smooth & light. Add flour, baking powder, baking soda & salt & mix
just until combined. Transfer batter to pan. Smooth out with
spatula. Arrange apple slices, overlapping, in a circle around outer
edge, filling in center with slices tucked attractively into place to
cover batter. Dot with remaining butter. Combine remaining 1/4 cup
sugar & 1/2 tsp. cinnamon. Sprinkle over apples. Bake until well
browned & wooden pick inserted into center comes out clean, about 1
hour. Cool in pan for 10 minutes. Use knife to loosen cake from sides
of pan & remove sides of pan. Serve warm. Can be made a day ahead &
refrigerated once it is completely cooled, uncovered. Reheat,
uncovered, in 350 oven until barely warm, not hot, about 10 minutes.