Boo! You don't have to wait until Halloween to make these festive and fun red velvet cakes. They're sure to be a hit with kids at birthday parties (and grown-ups, too)!
Preheat the oven to 350 degrees. Coat twelve 8-ounce mason jar tins with baking spray.
Sift together the flour, salt, and the cocoa and set aside.
In an electric mixer, beat the butter until soft and fluffy. Add the sugar and continue beating until everything is well combined and again, fluffy. Add the eggs 1 at a time and mix until each is well combined into the batter. Add the vanilla and mix well to combine, scraping down the sides if necessary.
In a separate bowl, whisk together the buttermilk and the food coloring, completely dissolving the dye into the buttermilk (otherwise it will sit on the bottom of the bowl).
Next, alternate between adding the flour and the buttermilk to the butter mixture in 3 parts, beginning and ending with the flour. Keep mixing the entire time, and scrape down the sides of the bowl to make sure that all of the butter and flour are mixed into the red batter.
Then, in a small bowl, add the vinegar and baking soda and mix it with a spoon to combine. Right after it fizzes up, add it to the batter, folding in with a spatula until well combined.
Immediately spoon the batter into the mason jars. (The batter is pretty thick, so using an ice cream scooper may be easier than using a spoon.) Bake the cakes for 20 minutes. Pull the cakes out and let them cool before frosting.
In the bowl of an electric mixer, whisk the eggs and salt until pale and frothy.
Meanwhile, add the sugar, corn syrup, water, and vanilla bean paste to a small pot. Cook over medium heat until the sugar is dissolved and just simmering, about 5 minutes.
With the mixer on medium speed, add a tiny bit of the hot sugar mixture to the egg whites at a time. (Make sure to do this slowly, or you'll scramble the eggs.)
Once all the sugar is incorporated, turn the mixer up to high. Beat the mixture on high for about 5 minutes or until very stiff and shiny.