Coat the bottom and side of a 9-inch round cake pan with 2 tablespoons butter; sprinkle the bottom of the pan with brown sugar.
ASSEMBLE THE APPLES:
In a medium bowl, toss the apples with lemon juice; arrange the apples in the prepared pan in two concentric circles (you might not use all of them).
PREPARE THE CAKE BATTER:
In a separate bowl, whisk together the flour, baking powder, cinnamon and salt; set aside.
In another bowl, use an electric mixer to beat the butter with the sugar until light and fluffy. Add the eggs and vanilla; beat until incorporated. With mixer on low speed, alternately add the flour mixture in three parts and the milk in two, beginning and ending with the flour mixture.
Spoon the batter over the apples in the pan; smooth the top. Bake until a toothpick inserted into the center comes out clean, 35 to 45 minutes. Cool the cake in the pan on a wire rack, at least 30 minutes and up to 6 hours (if the cake has risen above the rim of the pan, simply push it gently back inside the rim).
To serve, run a knife around the edge of the pan, and invert the cake onto a rimmed platter.
Notes
*This is a super easy cake to make. Watch the time- if you bake too long, it might be dry.
Be sure to arrange the apples carefully so that it decorates the top when it's flipped over.