Preheat the oven to 350°F. Place two cupcake liners in a muffin pan and spray with canola oil. Set aside.

Beat the canola oil, egg, milk, vanilla extract, and sugar together.

Add in the flour and baking powder.

Place 2 teaspoons of batter into 6 small cups. Place a drop of food coloring into separate bowls, allowing one bowl to be one color. Stir until combined and even.

Starting with the red batter, divide the batter in half (1 teaspoon per cupcake) and pour directly into the center of the cupcake liner in a even stream. Repeat with the remaining colors in the following order: red, orange, yellow, green, blue, and purple.

Gently place the muffin pan in the oven. Bake for about 15 minutes, or until a cake tester comes out clean.

To make the frosting, beat the butter and cream cheese together until combined. Beat in the vanilla and powdered sugar until combined.

Decorate your cooled cupcakes!