Make the Raspberry Filling: Combine raspberries, sugar, cornstarch, lemon juice, and vanilla in a saucepan. Cook over medium heat for 8–10 minutes until thickened and glossy. Let cool completely.

Make the Dough: In a stand mixer, combine flour, sugar, yeast, and salt. Add milk and eggs, mixing until combined. Gradually beat in softened butter, one tablespoon at a time, until the dough becomes smooth and elastic (10–12 minutes).

First Rise: Place the dough in a greased bowl, cover, and let rise until doubled, about 1½ to 2 hours.

Shape the Loaf: Roll dough into a 10×14-inch rectangle. Spread raspberry filling evenly, leaving a small border. Roll tightly from the long side, then cut the roll lengthwise. Twist the two halves together, keeping the cut sides up.

Second Rise: Transfer to a greased loaf pan, cover, and let rise again for 45–60 minutes, until puffy.

Bake: Preheat oven to 350°F (175°C). Brush with egg wash and bake for 30–35 minutes until golden brown and sounds hollow when tapped. Tent with foil if browning too quickly.

Cool & Serve: Let cool 10 minutes in the pan, then transfer to a wire rack. Cool completely before slicing.