Lemon Cupcakes with Passion Fruit Filling

Light, lemony cupcakes filled with tart and tangy passion fruit curd.  Buttercream peonies sit on top of a swirl of passion fruit frosting.  It doesn't get any prettier or tastier than this!

Passion fruit is one of my all-time favorite flavours.  From cake to popsicles, I love the sweet and tart flesh of a bright and sunny passion fruit.  But unless you live in Australia, where I ate passion fruit EVERYTHING with reckless abandon in my early twenties, or maybe Hawaii, passion fruit is not only difficult to find but comes with a hefty price tag. 

My family comes from Hawaii, so I've always had a taste for tropical flavors.  Mango, guava, sweet pineapple - I love it all!  But one fun way to challenge myself when creating new recipes is to pair unexpected flavors together.  In my new book, you'll find passion fruit mixed with nearly burnt caramel as well as a passion fruit French opera cake with chocolate hazelnut ganache.  Mmmm.....  Anyways, this time I went for something a bit in between.  Not too exotic in either direction.  Mixing two tart ingredients together proved to be exactly what late spring and summer needed.

While I've worked with real deal passion fruit flesh before, this recipe calls for passion fruit concentrate.  One, the whole fruits are very expensive up here in Canada.  And two, the concentrate works just as well, deliveries huge flavor, and you don't need to worry about all the seeds.  Passion fruit concentrate has been added to my favorite Swiss meringue buttercream.  I also used it to replace some the lemon juice from my favourite lemon curd to create a punchy filling for the cupcakes.  

The cupcakes themselves are super light and fluffy.  Massaging the lemon zest with the sugar before you start mixing releases all of the oils in the lemon zest to really flavor the cupcakes.  I use an apple corer to remove the center of each cake before filling, but you could also use a small paring knife or even a large piping tip, turned upside down.  The curd filling somewhat melts into the cake, so don't be shy when filling them up.

And yes, I know - there is a lot of buttercream going on here.  But peonies are finally in bloom and I wanted to practice my piping.  Using a similar technique as a buttercream rose, I use a Wilton 116 tip for the frilly peony-like flowers.  I used a #103 tip for the "closed" buds.  A few spring green leaves brings the flowers to life.

Instead of piping the flowers directly onto the cupcakes, I pipe them, using a flower nail, on cut squares of parchment paper.  I then chill the piped blooms in the refrigerator until the buttercream hardens.  From there, gently peel off the parchment paper and place them on the prepared cupcakes.

Passion Fruit Curd
makes about 1 cup

3 egg yolks
½ cup + 1 tablespoon sugar
3 tablespoons passion fruit concentrate, thawed
1 tablespoon fresh lemon juice
4 tablespoons unsalted butter, diced

Whisk together the egg yolks, sugar, passion fruit concentrate, and lemon juice in a small saucepan. Heat the mixture over medium heat.  Gently stir consistently until the mixture thickens and registers 160F on a candy thermometer, about 6 to 10 minutes.  Adjust the heat as needed, taking care not to curdle the eggs.

Once hot, remove the curd from the heat and strain, using a fine mesh sieve, into a heat-safe container.  Stir in the butter until smooth.  Place a piece of plastic wrap directly on the surface of the curd.  Refrigerate the curd until cool and thick, 2 hours or up to 1 week.

Lemon Cupcakes
makes about 24 to 28 cupcakes

1½ cups plus 2 tablespoons all-purpose flour
1½ cups  cake flour
1 tablespoon baking powder
½ teaspoon baking soda
½ teaspoon salt
2 tablespoons fresh lemon juice
1¼ cups milk
2 cups  granulated sugar
1 tablespoon lemon zest
1 cup unsalted butter, at room temperature
1 teaspoon pure vanilla extract
2 large egg whites
2 large eggs

Preheat the oven to 350°F. Line two cupcake pans with paper liners.

Sift together the flours, baking powder, baking soda, and salt into a large bowl. In a liquid measuring cup, add the lemon juice to the milk.  Stir gently and set aside.  In a small bowl, rub the sugar and lemon zest together between your fingertips until fragrant.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed for 2 minutes. Add the sugar-zest mixture and mix on medium-high until light and fluffy, 3 to 5 minutes. Stop the mixer and scrape down the bowl.

Turn the mixer to medium-low and add the  vanilla. Add the egg whites and eggs, one at a time. Stop the mixer and scrape down the bowl.

Turn the mixer to low and add the flour mixture in three batches, alternating with the milk mixture, beginning and ending with the flour mixture. After the last streaks of the flour mixture are combined, mix on medium for no more than 30 seconds.

Evenly divide the batter among the cupcake liners using a disher or mechanical ice cream scoop. Bake the cupcakes for 20 to 23 minutes, until a toothpick inserted into the center of a cupcake comes out clean.  Allow cupcakes to completely cool on a wire rack before filling and frosting.

 

Passion Fruit Buttercream
makes about 3 ½ cups

1 small batch Swiss meringue buttercream
3 to 4 tablespoons passion fruit concentrate, thawed, or according to taste

Omit the vanilla beans from the recipe and prepare the Swiss meringue buttercream as directed. With the mixer on medium-low, slowly add in the passion fruit concentrate and mix until combined.

 

Assemble the Cupcakes

Once the cupcakes have completely cooled, remove the centers using an apple corer, small paring knife, or a large piping tip (turned upside down).  Do not press all the way down to the bottom.  Reserve the cupcakes "centers" and set aside.

Use a spoon, piping bag, or zip-top bag with the corner snipped off to fill the cupcakes with the passion fruit curd.  Trim the reserved cupcake centers and gently replace on top of the curd.

Frost the filled cupcakes with the passion fruit buttercream.

 

For more tips on how to pipe buttercream flowers, click here