Apple Blackberry Cake

Name: Apple-Blackberry Cake
Ingredients: 1 1/2 cup Unbleached All-Purpose Flour; 2 tsp Baking Powder; 1/2 tsp Salt; 3 oz unsalted butter, melted, plus more for pan, plus 1 ounce cut into pieces; 3/4 cup packed light brown sugar; 2 tbsp packed light brown sugar; 1/2 cup Whole Milk; 2 x large eggs; 3 x Gala Apples, peeled, cored, and cut into 8 wedges; 1 cup Blackberries; 1/4 tsp ground cinnamon