In a microwave-safe container, gently heat whole milk and unsalted butter until the butter melts. Combine with instant yeast and granulated sugar, letting it sit until frothy.

In a stand mixer, mix the egg, milk mixture, flour, and salt on low speed. Then increase to medium and knead until smooth.

Shape the dough into a ball, place in a greased bowl, cover, and let rise in a warm area until doubled in size.

Prepare the filling by combining sliced rhubarb, sugar, lemon juice, and cornstarch in a saucepan. Cook until thickened.

Roll the dough into a rectangle, spread the filling, roll tightly, and cut into rolls.

Place rolls in a greased pan, cover, and let rise until puffy.

Preheat oven to 350°F and bake rolls until golden brown and fragrant.

Prepare the glaze by whisking rhubarb filling with powdered sugar and lemon juice until smooth.

Drizzle the warm rolls with glaze and serve warm.