Grease a 9x13-inch pan. Warm buttermilk to 105–110°F.
Whisk warm buttermilk and sugar in a large bowl. Sprinkle yeast over.
Rest until foamy, 5–10 minutes.
Stir in melted butter and 2 cups flour until shaggy.
Add salt. Mix in remaining flour gradually to form a tacky dough.
Knead 8–10 minutes on a lightly floured surface until smooth and elastic.
Place dough in a greased bowl. Cover and let double, 60–90 minutes.
Combine softened butter, brown sugar, cinnamon, and salt into a paste.
Punch down dough. Roll into a 12x16-inch rectangle, long side facing you.
Spread filling evenly, leaving a 1/2-inch bare strip along the far edge.
Roll up tightly into a log. Pinch the seam to seal.
Slice into 12 rolls with floss or a sharp knife. Arrange in the pan.
Cover and let rise until puffy, 30–45 minutes. Preheat oven to 350°F.
Bake 22–26 minutes, until lightly golden and set in the center.
Beat cream cheese, powdered sugar, butter, vanilla, and buttermilk until smooth.
Spread icing over warm rolls. Serve.
Notes
Overnight option: After slicing, arrange rolls in the pan, cover, and refrigerate. Let sit 45–60 minutes at room temperature, then bake. Try swapping 1/2 cup flour with bread flour for chewier rolls, or add chopped pecans to the filling. Leftovers keep 2–3 days covered at room temperature; warm briefly before serving.This recipe is an original creation inspired by classic Delish Buttermilk Cinnamon Rolls flavors. All ingredient ratios and instructions are independently developed.