Preheat the oven to 350°F (180°C). Line a cupcake tray with cupcake liners. Set aside.
Sift the flour into a mixing bowl. Add the sugar, baking soda, salt and cocoa powder and mix together.
Prepare the vegan buttermilk by adding 1 Tbsp lemon juice into a measuring jug and then adding soy milk up to the 1 cup (240ml) line and allowing to sit for a minute to curdle into buttermilk.
Add the vegan buttermilk, vanilla extract, oil, vinegar and red gel food color to the mixing bowl and whisk briefly with a hand whisk to combine into a batter. Don't over-mix.
Divide the batter evenly between the cupcake liners.
Place into the oven and bake for 20 minutes or until a toothpick inserted into the center of one of the cupcakes comes out clean.
Allow to cool completely before frosting.
Add vegan butter, powdered sugar, cocoa powder, vanilla extract, red gel food coloring and 2 Tbsp soy milk to the bowl of your stand mixer. Starting at slow speed, gradually increase speed until the frosting is thick and smooth. If needed, add the extra soy milk.
Pipe the frosting on top of your completely cooled cupcakes and serve.