Warm the milk until lukewarm. Stir in sugar and yeast; let foam 5–10 minutes.
Whisk flour and salt in a large bowl. Pour in foamy yeast mixture and melted butter.
Mix until a shaggy dough forms, then knead until smooth and elastic, 8–10 minutes.
Knead in raisins just until dispersed. Shape into a ball.
Lightly oil a bowl. Place dough inside, cover, and let rise until doubled.
Stir brown sugar and cinnamon together for the filling.
Roll dough into a rectangle. Brush with melted butter and sprinkle cinnamon sugar, leaving a bare edge.
Tightly roll into a log, pinch seam, and set seam‑side down in a greased 9×5 pan.
Cover and rise until puffy above the rim, 35–45 minutes.
Brush top with milk. Bake at 350°F until deep golden and 195°F inside, 35–40 minutes.
Cool 10 minutes, then lift out. Cool completely on a rack before slicing.