A Red Velvet Cake is essentially a vanilla cake (with a mild chocolate flavor), dyed bright red and frosted with a slightly tangy cream cheese frosting. You can spot a red velvet recipe if it calls for cocoa powder, vinegar and buttermilk.
I have always questioned the use of vinegar in a Red Velvet. I don't use vinegar for any other cupcake recipes but red vevlet usually calls for it. A little internet research says that the acidic vinegar creates a chemical reaction with the baking soda to help the cake rise. I tested this out and yes, it is true that the vinegar helps the cupcakes rise but it rise too much, creating a dome-shaped top. I would stick to baking soda as the leavening agent. It works slowly but it works well.
The use of vinegar is also said to react with the buttermilk to draw out the red hue in the cocoa powder. I gave this a try and found this to be untrue. The vinegar did nothing, or if it did, it did very little to bring out any red from the cocoa powder. Further internet research says that cocoa powder nowadays are processed that the chemical reaction to draw out the red with vinegar is no longer possible, which explains my very dark brown result.
To get any red to show in a red velvet, you really have to use red food coloring and a lot of it. In the below recipe, I used two tablespoons of red food coloring, which gave me brownish red cupcakes once baked. Feel free to double that to achieve a redder color. I've found that vinegar brightens up the red coloring, but not by much. I can safely say omit the vinegar if you don't have any. If you do use vinegar for that tiny shade of difference, the taste of vinegar does not show up in the end product.
Ingredients (18 cupcakes)
1-1/3 cups all-purpose flour
1/2 teaspoon salt
1-1/2 teaspoon baking soda
3 tablespoons cocoa powder
1/2 teaspoon instant espresso powder
2 tablespoons red food coloring
4 tablespoons unsalted butter
1-1/4 cups white granulated sugar
2 large eggs at room temperature
2 large egg yolks at room temperature
1/3 cup sour cream
1/2 cup vegetable oil
2 teaspoons vanilla extract
1/2 cup hot water
Preheat oven to 350 F.
Whisk together the flour, salt, and baking soda. Set aside.
Whisk together cocoa powder, instant espresso powder and red food coloring. Set aside.
In a stand mixer, beat the butter and sugar together until fluffy.
Add the eggs one at a time, slowly mixing after each addition.
Add the sour cream, vegetable oil and vanilla extract. Mix until combined.
Add the flour mixture to the butter/sugar mixture a third at a time, mixing until fully incorporated after each addition.
Add cocoa powder mixture. Mix until combined.
Add the water. Mix until combined.
Fill cupcake liners 3/4 full.
Bake for 18 minutes or when toothpick inserted in middle comes out mostly clean. Allow cupcakes to cool completely before frosting.