Preheat oven to 350°F (165°C). Line standard muffin tins with paper liners.
For the cupcakes, in a medium bowl, sift together flour, sugar, baking soda, salt and cocoa powder. In a large mixing bowl using a hand-held electric mixer, gently beat together the oil, buttermilk, eggs, food coloring, vinegar and vanilla. Add the sifted flour mixture and mix until smooth and thoroughly combined.
Fill the cupcake liners ⅔ full with batter. Bake for 19-20 minutes, until a toothpick inserted in the middle of a cupcake comes out clean. Cool for 10 minutes in the pans on wire racks then remove the cupcakes and cool completely.
For the frosting, whisk together flour and water in a medium saucepan and cook over medium heat, stirring constantly, until the mixture becomes very thick and pudding-like. Cover and set aside to cool to room temperature (at least 2 hours).
Using a stand mixer fitted with the whisk attachment, beat butter, sugar and vanilla on high speed, scraping bowl with a rubber spatula occasionally, until lightened. Add the cooled flour mixture and beat on high until airy and fluffy. It should have a light and silky texture and with no remaining sugar crystals.
Frost the cupcakes with a butter knife or pipe on frosting with a large round tip swirling from the outside of the cupcake to the center. Add red sprinkles if desired.
Notes
It is recommended to mix this batter with a hand-held mixer and there is some splattering! Be sure to put away electronics and items you don’t want decorated with red dots. I also advise against wearing white when making these. ;-)A couple of tips about the frosting: cook the flour and water before you start making the cupcakes so the mixture has time to cool to room temperature. It has to be completely cool and not the slightest bit warm before you add it to the whipped butter and sugar. Sometimes this frosting looks curdled and takes up to 15 minutes of beating to come together. If it separates after you’ve made it, you can beat it again to bring back the fluffy texture.