In the bowl of a standing mixer, or large bowl with a hand mixer, beat the butter and sugar until fluffy, about 2 minutes.
Add eggs, one at a time, mixing just until blended after each addition.
In a separate bowl, whisk together flour, baking powder, baking soda, nutmeg, and salt.
Add flour mixture to butter mixture in two increments, but add the sour cream between the two flour mixture additions. Beat well between additions.
Mix well, scraping the sides of the bowl.
Spread batter into prepared 9 x 9 inch pan or other similar sized baking dish. Batter is a bit stiff but spreadable.
(I use Baker's Joy to prepare my baking pans.)
Stir together brown sugar, pecans and cinnamon.
Sprinkle over batter.
Cover pan with plastic wrap and refrigerate for 8 hours. (Can be refrigerated up to 12 hours if needed.)
When ready to bake, preheat oven to 350 degrees F.
Bake for 35 minutes or until a knife inserted in the center comes out clean.