1. Combine Dry Ingredients: In a microwave-safe mug (at least 12-ounce capacity), whisk together the all-purpose flour, granulated sugar, unsweetened cocoa powder, baking soda, and salt. Make sure there are no lumps and everything is well combined. This ensures an even distribution of leavening agents and flavor.

2. Add Wet Ingredients: Pour in the buttermilk, vegetable oil, vanilla extract, and white vinegar into the mug with the dry ingredients.

3. Introduce Red Food Coloring: Add the red food coloring. Start with 1/2 teaspoon and add more if you desire a deeper red hue. Gel food coloring often provides a more intense color.

4. Mix Until Just Combined: Using a fork, stir all the ingredients together until just combined. Be careful not to overmix; a few small lumps are fine. Overmixing can lead to a tough cake. The batter should be smooth and uniformly red.

5. Microwave the Cake: Place the mug in the microwave. Cook on high for 60-90 seconds. The exact time will vary depending on your microwave’s wattage. Start with 60 seconds, then check for doneness. The cake is ready when it looks set and springs back slightly when gently touched in the center. It should not be gooey.

6. Cool and Serve: Carefully remove the hot mug from the microwave. Let the mug cake cool for a minute or two before enjoying. This allows it to set a bit more and prevents you from burning your mouth.

7. Optional Topping: If desired, top with a dollop of cream cheese frosting for that classic red velvet experience. A sprinkle of powdered sugar or a few chocolate chips also make lovely additions.