How to make perfect Rainbow cake | Butter cream frosting | Cupcake recipe

Ingredients:-
For the Rainbow Cake Layers:-
5 cups all-purpose flour (500g)
2 ½ cups granulated sugar (550g)
1 tablespoon baking powder
½ teaspoon baking soda
1 teaspoon salt
6 large eggs room temperature
1½ cups vegetable oil (360ml)
1½ cups whole milk (360ml)
1 tablespoon vanilla extract
Food colouring (Purple, blue, green, yellow, orange, red)
For the Buttercream:-
3 cups unsalted butter softened (680g)
½ teaspoon salt
6 cups confectioners sugar (720g)
1 tablespoon Milk/cream room temperature (optional)
1 tablespoon vanilla extract
pink food colour
For sugar syrup:-
1/2 cup (100g) sugar
1/2 cup (120ml) water
1 teaspoon vanilla extract
For cupcakes:-
1 1/4 cups all-purpose flour (157g) plus 1 teaspoon for chocolate chips
1 1/4 teaspoon baking powder
1/2 teaspoon salt
1/2 cup (114g) unsalted butter, softened
3/4 cup sugar (150g)
2 large eggs, room temperature
2 teaspoons vanilla extract
1/2 cup (120g) buttermilk, or plain kefir, room temperature
100 grams chocolate chips
Sprinkles
pink food colour
cake board
8-inch round cake pans
100 grams Fondant
cupcake cases
Preheat the oven to 350°F