In a large bowl, beat butter (or margarine) and brown sugar until light & fluffy; beat in eggs. Lightly spoon flour into measuring cup; level off. Add flour, baking soda, cinnamon, nutmeg and salt; mix well. Stir in apples. Spread batter in greased pan. Batter will be very stiff.
Bake at 350F for 25-35 minutes or until toothpick inserted in center comes out clean.
Cinnamon Butter Sauce:
Combine all sauce ingredients in small saucepan. Heat over medium heat until butter melts and sauce is hot, stirring frequently. Serve warm sauce over warm cake.