Dutch Apple Coffee Cake

6 cups flour
1 1/2 tsp salt
3 Tbsp baking powder
2 cups sugar
1/4 butter or margarine
2 cups milk
1 Tbsp vanilla
9 apples, cored and sliced
6 Tbsp margarine
3/4 cup brown sugar
1 Tbsp cinnamon

Combine flour, salt, baking powder and sugar; cut butter into mixture. Mix together eggs, milk and vanilla; combine with flour mixture, stirring until well blended. Pour batter into 2.5" x 12.75" x 23" pan. Arrange apple slices (peel side up) on top of the batter. Combine melted butter, brown sugar and cinnamon; sprinkle over top. Bake 30-35 minutes at 400 degrees.