Onion Bialys

Directions

1. First, make the sponge: In a medium bowl, stir the flour and yeast to combine. Make a well in the center, add the water, and mix with a wooden spoon until it's homogenous—it may look a bit shaggy, but should be fully combined. Cover with plastic wrap and leave to ferment at room temperature for 1 hour. There should be plenty of bubbles on the surface when it's done!
2. While the sponge ferments, start to caramelize the onions for the filling: Heat the olive oil in a large skillet over medium heat. Add the onions to the pan and reduce the heat to low. Cook slowly, stirring occasionally, until the onions become golden brown, 30 to 35 minutes. Season with salt and pepper. Set aside to cool.
3. While the onions cook, make the dough: In the bowl of an electric mixer fitted with the dough hook attachment, mix the bread flour, yeast, and salt to combine, 15 seconds.
4. Add the sponge and the water and mix on low speed for 2 minutes. Raise speed to medium and mix for 7 minutes more. Transfer the dough to a greased bowl, cover with plastic wrap, and let rise until nearly doubled in size, about 1 hour.
5. Line two baking sheets with parchment paper. Divide the dough into 12 even pieces. Gently stretch each piece into an oval shape, then transfer to the prepared baking sheets—6 on each sheet. Use your fingers to press the center of each piece of dough to flatten it; you're trying to make a cavity for the filling, with the outsides being a little thicker, kind of like pizza crust!
6. Cover the trays with greased plastic wrap and let rise for 30 to 45 minutes. Preheat the oven to 475° Fahrenheit.
7. Scoop 2 to 3 tablespoons of caramelized onions into the center of each piece of dough. Sprinkle 2 tablespoons of cheese on top of each piece.
8. Bake the bialys until they're golden at the base and around the edges—the cheese should be melty and golden too—about 16 to 20 minutes. Cool at least 15 minutes before serving.