1. In a large mixing bowl, combine the 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 about 1 hour or until doubled in size.
5. Preheat the oven to 475°F (245°C).
6. Punch down the dough and divide it into 8 equal pieces. Shape each piece into a ball.
7. Flatten each ball and make a depression in the center with your fingers.
8. In a small bowl, mix the chopped onions, poppy seeds, vegetable oil, and salt.
9. Fill each depression with the onion mixture.
10. Place the bialys on a baking sheet and bake for 12-15 minutes, or until golden brown.