Preheat your oven to 350°F (175°C). This ensures that your cake will bake evenly and rise perfectly.
Grease and flour your 9-inch round cake pans. This will help prevent the cake from sticking once it’s baked.
In a large mixing bowl, whisk together the all-purpose flour, sugar, salt, and baking soda until well combined. This step ensures that your dry ingredients are evenly distributed.
In another bowl, mix together the water, vegetable oil, white vinegar, and vanilla extract. Make sure everything is well combined.
Gradually pour the wet mixture into the dry ingredients, stirring gently until just combined. Be careful not to overmix, as this can lead to a tougher cake.
Divide the batter into two bowls. In the first bowl, add the yellow food coloring and mix well. In the second bowl, mix in the red food coloring. This will give you two vibrant colors to work with.
In your prepared cake pans, alternate spooning the yellow and red batter to create a marbled effect. Use a knife or toothpick to swirl the colors together for a magical look.
Place the pans in the preheated oven and bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.
Once baked, remove the cakes from the oven and let them cool in the pans for 10 minutes. Then, transfer them to a cooling rack to cool completely.