Preheat your oven to 200°F (95°C). In a large mixing bowl, combine 4 cups of all-purpose flour, 2 packets of instant dry yeast, 1 teaspoon of fine salt, and optional poppy seeds. Whisk until well-mixed.

Warm 1 cup of buttermilk, 1/2 cup of granulated sugar, and 1/2 cup of unsalted butter in a microwave-safe bowl for about 30-40 seconds. Stir gently to dissolve the sugar.

Pour the warm buttermilk mixture into the bowl with the dry ingredients and mix until a sticky dough forms.

Add 2 large eggs, one at a time, and fold in the zest of 4 lemons.

Gradually add 1-1.5 cups of all-purpose flour until the dough pulls away from the sides of the bowl and is slightly tacky.

Place the kneaded dough in a greased bowl, cover with a damp cloth, and let it rest for 10-20 minutes or until it doubles in size.

Mix together 1/2 cup of granulated sugar and 2 tablespoons of lemon zest in a small bowl for the filling.

Roll out the dough into a rectangle (12x18 inches) with an even thickness of about 1/4 inch.

Spread the filling mixture evenly over the rolled-out dough, leaving a small border.

Roll the dough tightly into a log and cut into 12 even pieces using dental floss.

Place the cut rolls in a greased baking pan and let them rise in the turned-off oven for about 30 minutes.

Preheat your oven to 350°F (175°C) and bake the rolls for 28-32 minutes until golden brown.

Whisk together 1 cup of powdered sugar, the juice of 1 lemon, and 2 tablespoons of melted butter until smooth.

Allow the rolls to cool for about 10 minutes before drizzling the icing over the top.