Heat the whole milk in a medium pot over low heat until it reaches 100°F. Remove from heat and add the active dry yeast and 1/2 teaspoon granulated sugar. Give it a quick stir. Let sit until foamy, about 5 to 10 minutes.
While the yeast is proofing, melt the unsalted butter and let it return to room temperature. Once cooled, whisk in vanilla extract and egg yolk until smooth. Pour this mixture into the base of a stand mixer along with the remaining 1/3 cup granulated sugar. Pour the activated yeast and milk mixture into the bowl of the stand mixer. Mix everything until combined.
Add all-purpose flour and salt on top. Mix on low speed with the dough hook until thick and slightly sticky (about 2 minutes), scraping the sides with a spatula as needed. Knead on medium speed until the dough gathers around the hook (about 5 to 6 minutes). If the dough is not gathering around the hook, you can slowly add additional flour (1/4 cup up to 3/4 cup extra).
Remove the dough and shape it into a ball. Grease the mixing bowl with cooking spray or butter and return the dough to the bowl, turning to coat. Cover with plastic wrap or a towel and let rise until doubled (about 45 mins to 1 hour 15 minutes).
Lightly flour a clean surface and roll out the dough to a rectangle shape (approximately 15 x 12 inches). Avoid overworking the dough.
With a table knife, spread the unsalted butter evenly over the dough (leaving a 1-inch border). Combine granulated sugar and zest from lemon until fragrant. Add 1/2 tablespoon lemon juice and mix. Sprinkle this lemon sugar over the butter. Sprinkle and gently press the fresh blueberries evenly over the mixture.
Cut the roll of dough into 12 equal slices and place (cut side up) in a well-greased 9×13-inch ceramic or glass pan.
Preheat oven to 375°F. Cover the rolls in the pan and allow them to rise until nearly doubled (about 20–30 minutes).
Warm the heavy cream for 15–20 seconds in the microwave. Using a pastry brush, brush the cream over the risen rolls and allow it to soak in.
Bake sweet rolls at 375°F for 30–35 minutes, until rolls are lightly golden brown at the edges and the centers are cooked through.
While the rolls are cooling, prepare the glaze by whisking together the zest of a lemon, 3 tablespoons lemon juice, melted unsalted butter, powdered sugar, and salt.
Allow sweet rolls to cool at room temperature for 5 to 10 minutes, then spread the glaze evenly over the rolls. Enjoy warm!
