Preheat oven to 350°F / 175°C and grease a 9×13-inch baking dish
Whisk together flour, baking powder, and salt
Add milk and melted butter, stir into soft dough
Knead lightly for 30 seconds
Roll dough into ¼-inch thick rectangle (about 12 × 16 inches)
Spread softened butter over dough
Sprinkle sugar and cinnamon over butter
Roll dough tightly into a log
Slice into 1½–2 inch thick pieces
Place slices in baking dish with small gaps between them
Heat milk or water, sugar, butter, vanilla, and salt until butter melts and sugar dissolves
Pour hot syrup around and between rolls until halfway up the sides
Bake for 45–55 minutes until golden, bubbling, and syrup is thickened
Let stand for 10–15 minutes before serving
Serve warm and scoop generously
