Grease the bottom and 12 inch up the sides of a 13x9x2-inch baking pan; set aside. In a large bowl, combine flour, baking powder, baking soda, and salt; set aside.
In a large mixing bowl, beat butter on medium speed with an electric mixer for 30 seconds. Add granulated sugar; beat until combined. Add eggs, one at a time, beating well after each addition. Beat in ricotta cheese. Beat in as much of the flour mixture as you can. Using a wooden spoon, stir in any remaining flour mixture. Spread batter in the prepared pan.
For topping, in a small bowl, combine nuts, brown sugar, wheat germ, cinnamon, and nutmeg. Sprinkle evenly over batter in pan. Chill, covered, in the refrigerator for up to 24 hours.
Preheat oven to 350 degrees F. Uncover coffee cake. Bake for 35 to 40 minutes or until a wooden toothpick inserted near the center comes out clean. Cool slightly in pan on a wire rack. Serve warm.