Cream butter, then gradually add sugar, beating well at medium speed with an electric mixer. Add egg and beat until blended. Combine flour, salt, cinnamon and nutmeg and mix well. Add to creamed mixture. Beat on low speed until smooth. Stir in water and vanilla. Fold in apples and pecans and spoon into greased and floured 9-inch pie pan.
Bake at 350 degrees for 45 minutes or until a toothpick inserted in the center comes out clean.
For filling: Combine brown sugar, sugar, butter and cream in a small saucepan and mix well. Bring to a boil and cook for 1 minute. Stir in rum. Serve warm or at room temperature with cake and whipped cream.
SERVES: 6 - 8