Start by preheating your oven to 350 degrees F. It's important to have the oven at the right temperature before you begin baking. But while it heats up, take a 12-cup bundt pan and spray it generously with nonstick spray to ensure your cake releases easily after baking.
Next, in a medium mixing bowl, whisk together the flour, baking powder, salt, and baking soda. This is a crucial step that helps to evenly distribute the leavening agents throughout the flour, ensuring a perfect rise.
In a separate larger bowl, use a hand mixer to combine the sugar, butter, and oil on medium speed for about four minutes. You want the mixture to be light and fluffy, which means you’re incorporating air into the batter. Once it’s nice and creamy, it’s time to add the eggs.
Beat in the eggs, one at a time, ensuring they are fully incorporated before adding the next. Then mix in the vanilla extract and continue beating for another two minutes. This helps to build a lovely, rich flavor in your cake.
Now, it’s time to alternate adding the flour mixture and the buttermilk into your wet ingredients. Start by adding one third of the flour mixture, then half of the buttermilk. Repeat this until everything is combined, beating until just incorporated. Be cautious not to overmix; you want your cake to be light and fluffy.
Once your batter is ready, divide it equally among six small bowls, aiming for about 1 1/3 cups in each bowl. This is where the fun begins! Start by adding the red food coloring to one bowl, stirring until the color is even. Repeat this process with the remaining colors (orange, yellow, green, blue, and purple), ensuring the colors are vibrant.
Transfer the first colored batter (red) into the prepared bundt pan, spreading it evenly using a spoon or an offset spatula. Follow with the other colors in the order you prefer. Try to layer each color evenly without swirling them together; the magic happens in the oven!
Once all the colors are in the pan, bake your cake in the preheated oven for 55 to 65 minutes. You’ll know it’s done when it’s puffed, golden brown, and a toothpick inserted into the center comes out clean. Patience is key here!
Let the cake cool in the pan for about 10 minutes before carefully inverting it onto a wire rack to cool completely. This step is crucial for maintaining its shape and ensuring a smooth finish.
In the meantime, prepare the glaze by whisking together the powdered sugar, lemon zest, and lemon juice until smooth. You might need to adjust the consistency by adding more lemon juice, one teaspoon at a time, until it’s thick but pourable.
Once the cake is completely cooled, pour the glaze over it, allowing it to drip down the sides beautifully. Let it set for at least 15 minutes before slicing and serving. Your Rainbow Bundt Cake is now ready to be enjoyed!
