Preheat your oven to 375°F. Line a muffin pan with paper liners and set aside.

In a large mixing bowl or stand mixer, cream together the butter and sugar until light and fluffy.

Beat in the egg and vanilla until combined. It’s okay if the mixture looks a bit lumpy.

In a separate bowl, whisk together the flour (except the extra tablespoon), baking powder, and salt.

Gradually add the buttermilk and flour mixture to the butter mixture, alternating between the two until fully incorporated. Scrape down the sides of the bowl as needed, and beat until the batter is smooth.

In a small bowl, toss the raspberries with the reserved tablespoon of flour, ensuring they are evenly coated. Gently fold in either half or all of the raspberries, depending on your preference (see notes).

Spoon about 1/4 cup of batter into each muffin liner. Top the muffins with the remaining raspberries.

For the crumble topping, mix the crumble ingredients in a separate bowl until they form a crumbly texture. Sprinkle the crumble generously over the tops of the muffins.

Reduce the oven temperature to 350°F and bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean, aside from any raspberry juice.