Step 1

Prep a small mixing bowl by adding the cubed butter to it, along with a fine mesh sieve. Set aside.

Step 2

Add the sugar to a small saucepan, then zest the lemon zest into the pan. Use your fingers to rub the zest into the sugar.

Step 3

Add in the lemon juice, egg yolks, and salt.

Step 4

Set the saucepan over medium heat, stirring constantly (this can be slowly - we just need constant movement happening!)

Step 5

Continue to stir the curd until it thickens and reaches a temperature of at least 170°F / 76°C (This took me about 3-5 minutes.)

Step 6

Remove the curd from the heat and pass it through the fine mesh sieve, over the butter. Mix the curd and the butter together until the butter has melted and the mixture is smooth. Transfer the curd to the fridge until you're ready to assemble the cupcakes.

Step 7

Preheat the oven to 350°F / 175°C. Line a cupcake pan with 6 parchment cupcake liners.

Step 8

To a medium sized mixing bowl, add in the sugar. Zest the lemon into the sugar, then use your fingers to rub the zest into the sugar.

Step 9

Add in the flour, baking powder, salt, and cubed butter. Use a hand mixer or a stand mixer fitted with the paddle attachment to beat the mixture together until the butter has completely combined with the dry ingredients and no lumps remain.

Step 10

Add in the oil, egg white, vanilla extract, sour cream, and milk. Whisk the ingredients together just until a cohesive batter has formed.

Step 11

Distribute the batter evenly between the six liners. Bake for 15-18 min., or until a toothpick inserted in the center of the cupcakes comes out with only a few moist crumbs.

Step 12

With a hand mixer or with a stand mixer fitted with the paddle attachment, beat together the cream cheese, butter, and salt until light and fluffy (~1 minute)

Step 13

Beat in half of the powdered sugar until it's combined, then beat in the other half. Add in the vanilla and beat for an additional minute, until the frosting is light and fluffy.

Step 14

Use a teaspoon measurement to push down in the center of the cupcakes to form a hole. Fill each hole with lemon curd up until the top of the cupcake.

Step 15

Frost the cupcakes with the cream cheese frosting, then swirl extra lemon curd on top. Serve and enjoy!