In a small bowl, sprinkle the yeast over the warm water. Stir briefly to combine, then allow to sit at room temperature until frothy, about 10 minutes.
In the bowl of a stand mixer fitted with a dough hook or a large bowl, combine the bread flour, rye flour, and salt.
Slowly mix in the frothy water with yeast and beer to form a smooth, slightly wet dough.
Cover and refrigerate for at least 12 hours and up to 16 hours.
Remove the bowl from the refrigerator and place at room temperature, still covered, for 2 hours to bring to room temperature.
Place a baking stone on the center rack of the oven and a baking dish 1/2 filled with water on the bottom rack.
Preheat oven to 450˚F (230˚C).
Sprinkle a baker's peel with a layer of cornmeal.
Generously flour work surface. Scrape the dough onto the flour and form into an oval loaf about 10 inches (25.5 centimeters) long and 4 inches (10 centimeters) wide.
Transfer the loaf to the baker's peel with cornmeal, cover with a towel, and allow to rest at room temperature until puffed, about 1 hour.
Gently dust the top of the loaf with flour and make 2-3 slashes down the loaf about 1/4 inch (6 millimeters) deep with a sharp knife.
Carefully slide the loaf onto the preheated stone and bake until golden brown, 30-40 minutes.
Allow to cool to room temperature before slicing.