Rainbow donut

Preparation

1. In the planetary mixer, process the softened butter at room temperature with the sugar until smooth.
2. Add grated lemon zest and proceed by adding 2 eggs at a time. Knead the dough well after adding each pair of eggs.
3. Sift the flour with the yeast and add two-thirds of the flour to the dough and half of the warm milk. Continue working the dough, alternating milk and flour, until both ingredients are completely used up.
4. Divide thedough equally into 3 bowls and for each add the powdered dye, first dissolving it in very little water. Mix all three mixtures well until the color is well blended.
5. Butter and flour a 27-cm-diameter doughnut mold.
6. Pour the three colored doughs into the mold with the help of a spoon: proceed clockwise, and when the first layer is finished, continue with the second layer of another color, alternating the three colors until all the doughs are used up.
7. Bake the bundt cake at 170° for 50 to 60 minutes; check for doneness with a toothpick. Once the cake is cooked, remove from the oven and let cool.
8. For the frosting: Dissolve one teaspoon of Gusto Yellow in warm water and process with previously sifted powdered sugar until smooth.
9. Pour the icing into a piping bag and decorate the surface of the doughnut, after which finish with colored sprinkles.

Thanks to Elena of Sweet Pink Sauce for the recipe.