Preheat oven to 350°F; grease 9x13-inch pan. Mix flour, baking powder, baking soda, and salt. Beat butter, sugar; add eggs, vanilla, sour cream. Add dry ingredients.
Mix brown sugar, cinnamon for filling.
Mix flour, brown sugar, cinnamon, melted butter, and pecans for streusel. Taste and adjust the sweetness.
Spread half the batter in the pan, add filling, top with remaining batter, then streusel.
Bake 30–35 minutes until a toothpick is clean. Cool 15 minutes.
Serve on a white ceramic platter with powdered sugar, berries, and coffee.