Follow these steps to create your Raspberry Swirl Brioche Loaf:

1. Mix Dry Ingredients: In a large bowl, whisk together the flour, sugar, salt, and instant yeast until well combined.
2. Combine Wet Ingredients: In a separate bowl, whisk together the warm milk, eggs, softened butter, vanilla extract, and lemon juice until smooth.
3. Combine Mixtures: Gradually add the wet ingredients to the dry ingredients, mixing until a dough forms. Knead the dough on a floured surface for about 8-10 minutes until it becomes smooth and elastic.
4. First Rise: Place the dough in a greased bowl, cover it with a damp cloth, and let it rise in a warm place for about 1 hour or until it doubles in size.
5. Prepare Raspberry Filling: While the dough is rising, prepare the raspberry filling. If using fresh raspberries, gently mash them with a fork. If using raspberry jam, simply set it aside.
6. Shape the Loaf: Once the dough has risen, punch it down and roll it out into a rectangle about 1/2 inch thick. Spread the raspberry filling evenly over the surface of the dough.
7. Roll and Cut: Starting from the long side, roll the dough tightly into a log. Pinch the seam to seal. Then, cut the log lengthwise down the center to expose the filling. Twist the two halves together and place them in a greased loaf pan.
8. Second Rise: Cover the loaf with a cloth and let it rise again for about 30-45 minutes until puffy.
9. Preheat Oven: Preheat your oven to 350°F (175°C).
10. Egg Wash: Brush the top of the loaf with a beaten egg for a golden finish.
11. Bake: Place the loaf in the oven and bake for 30-35 minutes or until golden brown and a toothpick inserted in the center comes out clean.
12. Cool: Remove the loaf from the oven and let it cool in the pan for 15 minutes, then transfer it to a wire rack to cool completely.

By following these steps, you’ll create a delicious Raspberry Swirl Brioche Loaf that is sure to impress!