Firstly preheat the oven to 350 degrees Fahrenheit
Place parchment paper in a 7-inch pan and grease with butter spray
Add all-purpose flour, milk powder, baking powder, baking soda, and salt in a wide vessel and mix well
Pour milk in a microwave-safe bowl and microwave for 2 minutes, keep it aside
Take sugar and oil in a separate bowl and mix well
Add vanilla extract and mix well
Furthermore, pour the hot milk into the oil-sugar bowl and mix well
Transfer the wet ingredients into the dry ingredients bowl and mix gently. Avoid overmixing
Equally Split the cake batter into 5 portions, each portion about 1/2 cup
Add food color of your choice to each portion and mix well
Gradually pour one portion at the center. let the batter spread on its own. Avoid tilting
Pour the second portion on top of the first portion at the center; let it spread on its own and form concentric circles
Repeat the concentric circles with the remaining colors
Avoid tilting the cake pan
Bake for 30-35 minutes until a toothpick inserted comes out clean
Cool the cake for 10 minutes then invert and unmold the cake. cool the cake completely