Activate the yeast: Heat up half of the milk until lukewarm. Add the sugar and active dry yeast to it and mix.
Mix the ingredients: Mix the butter, lemon zest, the remaining milk, salt, sugar, yeast, and eggs until smooth. Measure the flour into a large bowl.
Knead the dough: Now the hard work starts. Add your liquid mixture to the flour and knead it until all the flour is worked into the dough and it does not stick to your bowl anymore. By hand, this will take you 10 to 15 minutes. Once done, let the dough rest for 2 hours.
Roll the dough: After the dough has doubled in size, you can take it out, give it a brief knead, and separate it into three equal portions. Roll those portions into long strings.
Braid the loaf: Get your three long strands together on one side. Start by folding the right strand into the middle, then fold the left strand into the middle, then the right again, and so on—until you run out of dough.Put the braid onto a greased baking sheet (or use parchment paper) and let it rest for another 20 to 30 minutes. Apply the eggwash: While the dough rests, prepare the eggwash and preheat the oven to 350°F. Separate one egg yolk from a medium egg, add a pinch each of salt and sugar plus a splash of milk, and stir until smooth. Apply the eggwash generously onto the braid once it's well-rested. Sprinkle the pearl sugar on it.
Bake it: Put the braid into the preheated oven and bake for 30 to 35 minutes. You can check if it's done by tapping on it. If it sounds hollow, it's done.