Preheat over to 375°F and line a muffin pan with liners and set aside.
In a large mixing bowl or stand mixer, cream together the butter and sugar.
Beat in egg and vanilla until combined, the mixture will be a bit lumpy, that's okay.
Whisk together the flour (except the extra tablespoon, baking powder, and salt in a separate bowl.
Slowly add buttermilk and flour mix, alternating between each until incorporated in the butter mix. Scrape the sides of the bowl as needed. Beat the mixture until completely combined.
In a small bowl, toss the raspberries with the tablespoon of flour that was set aside earlier, making sure to coat. Then gently fold in about half OR ALL of the raspberries. See notes.
Add about 1/4 cup of batter to each muffin liner.
Load up the tops of the muffins with remaining raspberries.
In a mixing bowl, beat crumble ingredients until it looks like, well... a crumble. Sprinkle the crumble on the tops of the muffins.
Reduce oven heat to 350°F and bake muffins for 18-20 minutes. A toothpick should come clean from the center aside from potential raspberry juice.