Preheat the oven to 350º F (180º C). Line a cupcake pan with cupcake liners.
Combine flour, baking powder, salt, and cocoa powder in a bowl. Set aside.
In a mixing bowl or liquid measuring cup, combine milk and vinegar. Set aside.
Using an electric hand mixer or a stand mixer, beat butter until creamy and pale on medium-high speed, about 3 – 4 minutes. Add the sugar and beat on high speed for 2 minutes until creamed and pale, scraping down the sides and up the bottom of the bowl with a rubber spatula as needed. Then add oil and vanilla; continue beating to combine, about 1 minute.
Turn the mixer to low and add the flour mixture in three batches, alternating with milk mixture, beginning and ending with the flour mixture; beat until just combined, about 30 – 45 seconds. Add the food coloring and mix until just combined. Do not overmix.
Divide batter evenly among liners, about 3/4 full each.
Bake for 18 - 22 minutes on the same shelf, or until a toothpick inserted into the center comes out clean. Cool pan on wire racks for 5 minutes, then remove cupcakes from pan, place back on the rack, and cool to room temperature before frosting, about 1 hour.