1. In a large mixing bowl, combine flour, yeast, sugar, and salt. Gradually add warm water and mix until a dough forms.
2. Knead the dough on a floured surface for about 10 minutes until smooth and elastic.
3. Place the dough in a greased bowl, cover, and let it rise in a warm place for about 1 hour or until doubled in size.
4. Preheat the oven to 450°F (230°C). Punch down the dough and divide it into 8 equal pieces. Shape each piece into a ball and place on a baking sheet.
5. Flatten each ball slightly and make a depression in the center with your fingers.
6. In a small bowl, mix the chopped onions, poppy seeds, vegetable oil, and salt. Fill each depression with the onion mixture.
7. Bake for 15 minutes or until golden brown. Serve warm.