In a large mixing bowl, combine foamed active dry yeast with all-purpose flour, granulated sugar, and salt. Add softened unsalted butter, room temperature eggs, vanilla extract, and optional lemon zest to the mixture. Mix until a dough forms, then knead for 10-12 minutes until smooth.

Transfer the kneaded dough to a greased bowl; cover with a damp cloth and let it rise for 1-1.5 hours until doubled in size.

Prepare the raspberry filling by combining raspberry preserves, cornstarch, and water in a saucepan over medium heat. Stir until thickened, about 5 minutes. Cool while dough rises.

Punch down the risen dough and roll it out into a large rectangle. Spread cooled filling over the dough, then roll tightly into a log and pinch seams to seal.

Slice the rolled log lengthwise down the center, twist the two halves together and tuck the ends underneath. Place in a greased pan.

Cover loaf with a towel and let rise again for 30-45 minutes until puffy.

Preheat oven to 350°F. Brush loaf with melted butter and bake for 35-40 minutes until golden brown.

Cool in the pan for 10 minutes, then transfer to a wire rack. Mix powdered sugar with lemon juice and drizzle over the warm loaf.