Place the strawberries in a blender. Blend until the strawberries becomes a puree.
Pour the pureed strawberries in a medium saucepan, place over medium heat.
Bring to a simmer, and stir often.
Cook the puree until it reduces to ¾ to 1 cup. You will use ¼ cup for the cupcake batter, another ¼ for the curd, and another ¼ for the frosting, but it’s good to have a bit leftover just in case, so make it a heaping ¾ cup or a full cup.
It can take 10 minutes or a bit longer to reduce the puree. It depends on how high the heat is.
Remember to stir occasionally, and after pouring the puree into a heat-safe measuring cup, check the amount — if there’s still too much liquid, return it to the pan to cook a bit longer before measuring again.
Pour in a bowl and cover with plastic wrap directly on the surface of the puree so it doesn’t form a crust. Let the puree cool down completely before using it in the recipes. You can make it 1 day ahead and keep it in the fridge.
Preheat the oven to 350°F (175°C). Line a cupcake pan with liners.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In the bowl of a mixer, beat the butter for about 30 seconds until smooth. Add the sugar and beat for another 1–2 minutes, until slightly lighter in color.
Add the vegetable oil and lemon zest. Beat for 2 minutes, until the mixture looks creamy and emulsified.
Add the eggs one at a time, mixing well after each addition. Add the vanilla extract with the last egg.
Add the strawberry puree and mix until combined. If desired, add no more than one drop of pink food coloring to enhance the color.
Add half of the dry ingredients and mix on low speed just until incorporated. Add the buttermilk and mix. Add the remaining dry ingredients and mix just until combined. Do not overmix.
Divide the batter evenly among the cupcake liners, filling about ⅔ full.
Bake for 18–22 minutes, or until a toothpick inserted in the center comes out clean.
Remove from the oven and let cool completely before filling and frosting.
Beat the butter with an electric mixer for 1 minute in a mixing bowl. Add the granulated sugar and beat for another minute, until creamy.
Next, add the eggs, one at a time, and mix, making sure the first egg is incorporated before adding the next. Add the strawberry puree, the lemon juice, zest and salt and mix on low speed until combined. The mixture might look separated and that’s okay.
Pour it into a small saucepan with a heavy bottom and place it over medium-low heat.
Make sure you don’t let the curd come to a boil at any point, and don’t stop stirring at any point either, because that will lead to the eggs curdling, and the curd will taste like scrambled eggs.
Heat the curd slowly until a candy thermometer reads 170ºF (76ºC). If you don’t have a thermometer, the curd should be thick and coat the back of a spoon. Once you achieve a nice thick curd, strain it, and place it in a bowl. Let it come to room temperature, then place it in the fridge for at least 2 hours. The curd will set and get very thick as it cools.
Beat the butter in the bowl of a mixer for about 30 seconds until smooth.
Add the cream cheese and beat for another 30 seconds on medium speed until combined and creamy.
Add half of the powdered sugar and mix on low until incorporated. Increase to medium speed and beat briefly until smooth.
Add the remaining powdered sugar, reserving about ½ cup. Mix on low until combined.
Add the lemon zest and mix. Divide the frosting evenly between two bowls.
To one bowl, add the strawberry puree and mix until combined. Add an additional ½ to 1 cup powdered sugar as needed to thicken the strawberry frosting. Add a drop of pink food coloring if desired.
If needed, adjust consistency in both frostings by adding more powdered sugar until they are thick but pipeable.
Lay out a piece of plastic wrap on the counter. Spread the lemon frosting in a strip, and right next to it spread the strawberry frosting.
Roll the plastic wrap tightly into a log and place it inside a piping bag fitted with your desired tip. I used a 4B.
Once the cupcakes are completely cooled, use a small knife or cupcake corer to remove the center of each cupcake.
Fill the center with the chilled strawberry lemonade curd.
Pipe the frosting on top of each cupcake. Top with a halved strawberry and a lemon slice.
