Butter and lightly flour 13x9-inch baking pan or casserole dish. Set aside.
In a large bowl, whisk together 2 cups of flour, baking powder, baking soda, salt, and cinnamon. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or using an electric hand mixer), beat butter until smooth. Add sugar. Beat until well incorporated. Scrape down sides of the bowl as needed to ensure thorough mixing.
Add in eggs and sour cream. Mix until combined. With the mixer running on slow speed, add dry flour mixture in three additions. Mix until just combined.
Fold in berries, orange zest, and milk. Batter will be thick. Spread batter into prepared baking pan. Cover and keep in the fridge for 2 to 24 hours.