1. In a large mixing bowl, combine flour, yeast, sugar, and salt.
2. Gradually add warm water and mix until a dough forms.
3. Knead the dough for about 10 minutes until smooth and elastic.
4. Place the dough in a greased bowl, cover, and let it rise for 1 hour.
5. Preheat oven to 450°F (230°C).
6. Divide the dough into 8 pieces and shape each into a ball.
7. Flatten each ball and make a depression in the center.
8. In a pan, sauté onions in olive oil until soft. Add poppy seeds and salt.
9. Fill each dough depression with the onion mixture.
10. Place bialys on a baking sheet and bake for 15 minutes or until golden brown.