INGREDIENTS :
FOR THE VANILLA CUPCAKE:
180 g (1 ½ cups) cake flour
168g (¾ cup + 1 tbsp + 1 tsp) granulated sugar
2 teaspoons of baking powder
¼ teaspoon of salt
76 g (5 ½ tbsp) unsalted butter (room temperature)
65g (⅓ cup) oil*
113 g (½ cup) plain whole milk Greek yogurt (room temperature)
113 g (½ cup) whole milk (room temperature)
1 egg
1 teaspoon vanilla paste or extract
FOR THE VANILLA SWISS MERINGUE BUTTERCREAM:
145 g (about 4) egg whites
300 g (1 ½ cups) granulated sugar
½ teaspoon of salt
340g (1 ½ cups; 3 sticks) unsalted butter (room temperature, but cooler)
1 teaspoon vanilla paste or extract
rainbow jimmy sprinkles for decoration

INSTRUCTIONS :
FOR THE VANILLA CUPCAKE:
Preheat oven to 350 degrees F (180 degrees C). Grease and line two 6-inch cake pans with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, sugar, baking powder and salt.
Cut the butter into small cubes and add it to the dry ingredients. Mix on low speed until it resembles wet sand.
Add the oil, yogurt, milk, egg and vanilla and mix until well combined.
Divide the batter evenly between the prepared cake pans. (I recommend weighing the dough to be as accurate as possible!)
Bake for 28 to 32 minutes or until a toothpick inserted comes out clean.
Cool completely before frosting.
FOR THE VANILLA SWISS MERINGUE BUTTERCREAM:
In a double boiler, heat the egg whites, sugar and salt, whisking frequently until it reaches 160 degrees F (70 degrees C) or until the sugar is completely dissolved and until the egg whites are no longer grainy.

Transfer the egg white mixture to a bowl of a stand mixer with a whisk attachment. Whisk on high speed until stiff peaks form. Turn the mixer down to low speed and wait until the meringue cools to at least 85 degrees F (30 degrees C).
Cut the butter into cubes and add to the meringue a few pieces at a time, allowing them to fully incorporate before adding more. Once all the butter is added, it will probably look curdled, but keep beating for a few more minutes and it will come together.
Once the buttercream is almost smooth, replace the whisk with the paddle attachment and continue mixing on low speed until combined and smooth.
Add the vanilla and mix until completely incorporated.

FOR MOUNTING :
Secure the first cake layer to the cake stand with a small amount of frosting on the bottom. Use a cookie or ice cream scoop to measure the frosting for each layer. I used a 3 tbsp cookie scoop and put 3 scoops of frosting on each layer.
Cover the entire cake with a thin layer of frosting for the crumb coat.
Place in the refrigerator for about 20 minutes, then frost the cake as desired.
Top with Rainbow Jimmy Sprinkles and enjoy!

REMARKS :
You can use any neutral-tasting oil. My favorite is light-tasting extra virgin olive oil, but you can also use vegetable or canola oil.
You can make the cake layers the day before and decorate it the next day. Simply wait until the cakes are completely cooled, then wrap them tightly in plastic wrap and store them at room temperature.
I recommend making the buttercream the day you decorate the cake.
Cover the cake and leave at room temperature for up to 5 days. Yes, it stays wet that long!!!