In a large mixing bowl, cream butter and sugar. Add eggs, one at a time, beating well after each addition. Add extracts; mix well. Combine the flour, baking powder and salt; add to the creamed mixture alternately with eggnog. Pour into two 9 inch round baking pans coated with nonstick cooking spray. Bake at 350° for 30-35 minutes or until a tooth pick inserted near the center comes out clean. Cool for 10 minutes before removing from pans to wire racks.
For frosting, combine flour and salt in a saucepan. Gradually stir in eggnog until smooth. Bring to a boil over medium heat; cook and stir for 2 minutes or until thickened. Remove from the heat; cool to room temperature.
In a large mixing bowl, cream butter and sugar. Add eggnog mixture and vanilla; beat on high until fluffy. Spread frosting between layers and over top and sides of cake. Store in the refrigerator. Serves 12.