Step 1

Preheat your oven to 350°F. Line a muffin pan with nonstick cupcake liners and set aside.

Step 2

In a medium mixing bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

Step 3

In a separate small mixing bowl, whisk together the sour cream and buttermilk until completely combined. Set aside.

Step 4

Add the butter and sugar to the bowl of a stand mixer fitted with the paddle attachment. Cream the butter and sugar together until pale and fluffy, about 7-9 minutes, scraping down the sides and bottom of the bowl as needed. Start on low speed then gradually increase to a high speed of 8 or 9.

Step 5

Add the eggs to the bowl with the butter mixture one at a time and mix after each addition until fully mixed in. Beat in vanilla and blackberries until completely mixed in. Scrape down the sides and bottom of the bowl to ensure all the ingredients are combined.

Step 6

Use a cookie scoop to spoon batter into lined muffin cups, filling them about 2/3 full. Bake the cupcakes for 15-18 minutes, or until a toothpick inserted into the center comes out clean aside from a few moist crumbs.

Step 7

Cool the cupcakes in the pan for 10 minutes, then transfer to a cooling rack to cool completely.

Step 8

Make The Blackberry Buttercream

Step 9

Place the butter in the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed (setting of 4-until completely smooth and creamy, about 2 minutes. Add the blackberries to the bowl and beat until completely mixed into the butter, scraping down the sides and bottom of the bowl as needed.

Step 10

Add in the powdered sugar, beating in one cup at a time on medium speed, until the frosting is sturdy and smooth. If you feel that your frosting isn't thick or sturdy enough, beat in 1/2 cup more powdered sugar. Beat in the lemon juice until smooth.

Step 11

Spoon the frosting into a piping bag fitted with a large round piping tip and pipe frosting onto the completely cooled cupcakes in a swirl pattern, staring at the rim and working your way toward the center, coming to a peak.

Step 12

Garnish cupcakes with a fresh blackberry and serve at room temperature