Activate the yeast: Dissolve the fresh yeast in warm water and add a tablespoon of flour. Mix and cover with plastic wrap. Let it activate overnight.
Make the syrup: Combine water, lemon peel, and a cinnamon stick in a small saucepan and bring to a boil. Let the syrup cool.
In the mixer bowl, combine 500 g of T65 flour with 200 g of sugar, a pinch of salt, and a teaspoon of ground cinnamon.
Separate the egg yolks from the whites of the four eggs. Beat the egg whites until stiff peaks form.
Make a well in the center of the flour mixture and add the activated yeast from the previous day. Mix it a little. Then add the butter, olive oil, egg yolks, and a bit of the syrup (30 ml of water). Finally, fold in the beaten egg whites.
Beat the mixture in a mixer, using the dough hook, for at least 20 minutes. The dough should be elastic and develop gluten.
Sprinkle the counter with plenty of flour and place the dough on top. Using your hands, form the dough into a ball.
Grease a container with olive oil, insert the ball of dough, and grease the dough with olive oil so it doesn't dry out. Cover with plastic film.
Let the dough rise in a warm, covered place overnight.
The following day, after the dough has doubled in size, divide it into two equal-sized balls on a well-floured surface.
Roll each ball into a long shape, about 60 cm (24 inches) in length, then braid the dough and join the ends together to form a crown.
Place the braided crown on a baking tray lined with parchment paper. Brush it with a beaten egg.
Let the dough rest for 30 to 60 minutes.
Preheat the oven to 180°C (350°F) on the fan setting.
Bake the sweet bread for 30 minutes at 180°C (350°F). Cover it with aluminum foil during the last 15 minutes to prevent it from getting too dark.
After 30 to 40 minutes, remove the bread from the oven. The dough should be fully cooked inside; you can insert a toothpick to check if it comes out dry, though this may not always be definitive.