Lemon Blueberry Cupcakes are perfectly tender and moist with tons of fresh lemon and blueberry flavors, plus an easy swirled buttercream that will impress everyone!
In a medium bowl combine the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, use an electric mixer on medium-high speed to beat the butter and sugars until fluffy and very well combined, about 3 minutes. Scrape down the bottom and sides of the bowl. On medium-low speed, add the egg and yolk and beat until combined, scraping down the bowl as needed. Combine the buttermilk, lemon zest, and lemon juice. Add in the flour mixture and buttermilk mixture in alternating batches, starting and ending with the flour, mixing until just combined.
In a small bowl, toss the blueberries with the remaining 2 tablespoons of flour. Add into the batter and fold with a spatula until combined. Be very careful not to overmix, as that will create dense and gummy cupcakes.
Divide the batter among the prepared muffin tins, filling each 3/4 full. Bake for 15 to 20 minutes, or until a toothpick inserted in the center comes out clean. Allow the cupcakes to cool in the pan for 5 minutes before removing to a wire rack to cool completely.
Make the buttercream:
Using a blender, immersion blender, or food processor, puree the blueberries. Pass the pureed blueberries through a fine mesh strainer and into a medium bowl to remove the skins. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, mix together the sugar and butter. Mix on low speed until well blended and then increase the speed to medium and beat for another 3 minutes. Add the salt and vanilla and beat on medium for 1 minute.
Remove half of the buttercream to a bowl and add the blueberry puree gradually until the buttercream is well-colored and flavored but not too thin. If the buttercream does get too thin, add more powdered sugar to thicken.*
To the plain buttercream, add the cream and beat until well combined.
Swirled Piping:
In a large piping bag fitted with a decorative tip (such as the Ateco #846), use a spoon to scoop the plain frosting into one section of the bag, using your finger on the outside of the bag to help scrape it off. Repeat with the blueberry frosting. Ensure you’re aligning the frosting so it starts at the same place in the bag. Don’t worry if the colors touch each other.
Squeeze the bag to slightly blur the colors together for a watercolor type effect. Twist the bag and squeeze out a test pipe to ensure the colors are coming out evenly before piping onto your cupcakes. Garnish frosted cupcakes with lemon zest.
Serve or store at room temperature for up to 1 day, or in the fridge for up to 3 days. Let come to room temperature before serving.
Notes
*If desired, add a few drops of purple food coloring to enhance the pretty color of the blueberry portion of the buttercream frosting.