Preheat your oven to 200°F (95°C). In a large mixing bowl, combine flour, yeast, poppy seeds, and salt. In a saucepan, mix buttermilk, sugar, and butter until warm, then pour into dry ingredients. Add eggs, stir, and add lemon zest. Rest for 10-20 minutes.

In a medium bowl, combine granulated sugar, light brown sugar, and lemon zest. Add softened butter and whisk until smooth.

Dust a clean surface with flour, roll out dough into a rectangle, spread filling evenly, roll tightly, and cut into 12 pieces. Place rolls in a greased pan, cover, and let rise in turned-off oven for 30 minutes.

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

Prepare icing by whisking together powdered sugar, lemon juice, and melted butter until smooth.

Drizzle icing over slightly cooled rolls and garnish with lemon zest.