Preheat oven to 350.
Line an 8-inch cake tin or a loaf pan with parchment paper and set aside.
In a large mixing bowl, combine flour, baking powder, light brown sugar, melted butter, eggs and yogurt; mix until thoroughly combined.
Gently fold in the berries.
Pour mixture into prepared pan; set aside.
Add cold butter, oats, and light brown sugar in your food processor; pulse a few times until mixture is crumbly.
Sprinkle streusel on top of cake batter.
Bake for 75 to 80 minutes, or until a toothpick inserted in the center comes out clean.
Remove from oven and let stand 10 minutes.
Invert cake onto a cooling rack and let completely cool before cutting.