Preheat the oven to 350 degrees F. Grease a 9-inch by 13-inch baking pan.
In a large mixing bowl, combine the flour, sugars, salt, nutmeg, and oil by hand or on the lowest speed of a mixer. Reserve ½ cup for the topping. To the flour mixture left in the mixing bowl, add the eggs, soda, and buttermilk. Mix on the lowest speed until just blended. Pour into the baking dish. Sprinkle with the reserved topping, the nuts, and the cinnamon.
Bake for 40 minutes or until a tester inserted near the center comes out clean. Cool for at least 10 minutes before serving, or serve completely cooled.