Preheat oven to 350 degrees F. In a medium bowl stir together the flour, baking powder, and salt. In another bowl whisk together milk, honey, and vanilla.
Place 1/4 cup of the butter in a 9-inch square baking pan. Place pan in oven until butter melts. Stir in 1/2 cup of the brown sugar. Arrange 9 apple slices and the pecan halves in pan.
In a large bowl beat the remaining 1/4 cup softened butter with a mixer on medium to high 30 seconds. Gradually add the remaining 1/2 cup brown sugar, beating until light and fluffy. Add eggs; beat 1 minute. Add flour mixture and milk mixture alternately, beating on low after each addition just until combined. Carefully spread batter over apple slices in prepared pan.
Bake 35 to 40 minutes or until a toothpick comes out clean. Cool in pan on a wire rack 5 minutes. Loosen sides of cake; invert onto a plate. Cool 30 minutes; serve warm.