1. Prepare the Dough

1. Activate the yeast:
   In a small bowl, mix the warm milk with a pinch of sugar. Sprinkle the yeast on top and let sit 5–10 minutes, until frothy.

2. Mix dry ingredients:
   In a large bowl, whisk together the flour, sugar, and salt.

3. Combine wet and dry:
   Add the yeast mixture, softened butter, eggs, vanilla, and optional lemon zest. Stir until a shaggy dough forms.

4. Knead:
   Transfer the dough to a lightly floured surface. Knead 10–12 minutes until smooth and elastic. Add small amounts of flour only if the dough is too sticky.

5. First rise:
   Place the dough in a greased bowl, cover with a damp towel, and let rise in a warm place for 1–1½ hours, or until doubled in size.

2. Make the Raspberry Filling

1. In a small saucepan, mix raspberry jam, cornstarch, and water.

2. Cook over medium-low heat until slightly thickened.

3. Remove from heat and let cool completely.

3. Shape the Loaf

1. Roll out:
   After the dough has risen, punch it down and roll it into a 10×15-inch rectangle.

2. Add filling:
   Spread the cooled raspberry mixture evenly over the dough, leaving a ½-inch border.

3. Roll and slice:
   Roll the dough tightly from the long side into a log.
   Slice the log lengthwise to expose the layers.

4. Twist:
   Twist the two halves together with the cut sides facing up.

5. Second rise:
   Place the twisted dough in a greased 9×5-inch loaf pan.
   Cover and let rise for 30–40 minutes.

4. Bake the Loaf

1. Preheat the oven to 350°F (175°C).

2. Brush the top with melted butter.

3. Bake for 35–40 minutes until golden.
   If browning too quickly, tent with foil for the last 10 minutes.

4. Let cool in the pan for 10 minutes, then transfer to a wire rack.

5. Add the Optional Glaze

1. Whisk powdered sugar, lemon juice, and milk until smooth.

2. Drizzle over the cooled loaf.