Preheat oven to 375.
Line muffin pan with paper liners.
Whisk together 1/2 cup flour and 1/2 cup brown sugar.
Add in butter and use a fork to mix until crumbles form.
Stir together flour, baking powder and salt.
In another bowl, combine egg, sugar, sour cream, oil, and vanilla. Mix until blended.
Add wet ingredients to dry ingredients and mix until just combined.
Spoon batter into prepared pan.
Top each muffin with raspberries and then cover with streusel topping.
Bake about 20 minutes or until the toothpick inserted in the centre comes out clean.
Cool for 5 minutes in the pan then transfer to cooling rack.