In a large mixing bowl, combine 2 cups of flour, sugar, yeast, and salt. Mix until evenly distributed.

In a separate bowl, whisk together warm milk (110°F), melted butter, egg, and vanilla extract until well combined.

Pour the wet ingredients into the dry ingredients and mix with a wooden spoon until a shaggy dough forms.

Gradually add the remaining flour, 1/4 cup at a time, until the dough pulls away from the bowl sides and is slightly tacky to touch.

Turn the dough onto a lightly floured surface and knead for 8-10 minutes until smooth and elastic.

Place the dough in a greased bowl, cover with a kitchen towel, and let rise in a warm place for 1-1.5 hours until doubled in size.

Mix both sugars, cinnamon, softened butter, and vanilla extract in a small bowl until a thick paste forms.

Once the dough has doubled, punch it down and roll into a 9x18-inch rectangle on a floured surface.

Spread the cinnamon filling evenly across the dough, leaving a 1/2-inch border on all sides.

Tightly roll the dough from the short end into a log and pinch the seam to seal.

Place the rolled dough seam-side down into a greased 9x5-inch loaf pan. Cover and let rise for 45-60 minutes.

Preheat oven to 350°F (175°C) during the final 15 minutes of the second rise.

Brush the top of the loaf with melted butter or egg wash for a golden finish.

Bake for 35-40 minutes until deep golden brown and internal temperature reaches 190°F.

Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.