Grease a 9" cakepan; sprinkle with breadcrumbs, and tap out excess. Set pan aside.
Combine flour, sugar, salt, and butter with a pastry blender until crumbly. Remove 1 cup crumb mixture; set aside. Stir baking powder and 1/4 teaspoon nutmeg into remaining crumb mixture.
Stir together eggnog, egg, bourbon, and vanilla. Add eggnog mixture to crumb mixture; beat at medium-high speed with an electric mixer 2 minutes. Pour batter into prepared pan.
Combine brown sugar, cinnamon, and remaining 1/2 teaspoon nutmeg to reserved 1 cup crumb mixture; sprinkle over batter. Bake at 375° for 45 to 50 minutes or until a wooden pick inserted in center comes out clean. Serve warm or at room temperature.