How to Make It
Place the golden raisins in a small bowl and cover with hot tap water. Soak for 15 minutes before straining and patting dry with paper towels.
Heat 1 cup of milk for 20 seconds in the microwave. Check to make sure the temperature is between 105°F and 115°F. If it is too cool, microwave longer, and if it is too warm, stir to cool until it is within the proper temperature range. Add milk to the bowl of a stand mixer along with 1 teaspoon of the granulated sugar. Stir to dissolve sugar before adding the yeast. Stir with a fork until the yeast is dissolved. Allow to sit until the yeast sponge is very foamy, about 7 minutes.
While the yeast sponge is developing, mix together the flour, remaining granulated sugar, lemon zest, and salt in a medium bowl.
Once the yeast sponge is very foamy, add the flour mixture, eggs, 2 egg yolks, and melted butter. Using a dough hook attachment, mix on medium speed until a sticky dough forms that pulls away entirely from the sides of the bowl, scraping down the sides of the bowl as needed, about 6 minutes.
Remove dough to a lightly floured surface. Press the dough down with your hands into a rectangle that is about 1/2-inch thick. Spread raisins across half of the dough rectangle, fold the uncovered side over the side with the raisins, pressing the edges to seal. Then knead the dough into a ball for 4 minutes, allowing the raisins to incorporate into the dough. Place dough in a buttered bowl, turning the dough to coat in butter. Cover with plastic wrap and set in a warm place until doubled in size, 60 to 90 minutes.
Punch dough down and transfer to a lightly floured surface. Divide into 3 equal portions. Roll each dough portion into 26-inch long cylinders. Place these cylinders parallel to each other and braid.
Line a rimmed baking sheet with parchment paper. Grease the outside of an 8-oz. oven-safe ramekin with cooking spray, and place it upside down in the center of the baking sheet. Pick up the dough braid and transfer it to the baking sheet, wrapping it evenly around the ramekin, joining the ends of the braid together by pinching the dough together. Cover loosely with plastic wrap and transfer to a warm place to rise until puffy, about 25 minutes.
Preheat oven to 350°F while dough braid is rising. When the braid has finished rising, whisk together the remaining egg yolk with the remaining milk and brush the entire surface with the egg wash. Bake for 35 minutes or until golden brown and the internal temperature is 195°F, rotating halfway through baking.