In a medium mixing bowl, add the flour, sugar and salt for the streusel topping. Whisk to combine well.

Pour the melted butter into the dry mixture and mix with a fork until well combined, resembling sand. Set aside.

Add the melted butter, white sugar, eggs, buttermilk, sour cream and vanilla to a large mixing bowl, and beat with a whisk until smooth.

In a separate bowl, add the flour, baking powder, baking soda, and salt. Whisk to combine, then add to the wet mixture. Mix with a wooden spoon until just combined. Fold in the raspberries.

Cover the muffin batter and place into the fridge to rest for 4 hours to overnight for tall muffin tops.

Preheat oven to 425°F. Prepare a cupcake tin with liners.

Evenly disperse the batter into the cupcake liners with a medium cookie scoop, being careful not to deflate the batter.

Sprinkle the streusel topping on top of each muffin. Bake at 425°F for 6 minutes, then reduce the oven temperature to 350°F and bake for an additional 12 minutes, or until a toothpick comes out clean.