In a large mixing bowl, combine 250 grams of all-purpose flour (maida), 1/2 teaspoon of salt, 1/2 teaspoon of sugar, and 1/2 teaspoon of baking powder.
Add 2 tablespoons of oil and mix well. Gradually add 100 ml of lukewarm water and knead the mixture into a soft dough. Cover the dough with a damp cloth and let it rest for 30 minutes.
Meanwhile, prepare the onion filling by finely chopping 2 medium-sized onions, 2 green chilies, and a handful of fresh coriander leaves. Mix them in a bowl and add 1/2 teaspoon of red chili powder, 1/2 teaspoon of garam masala, 1/2 teaspoon of chaat masala, and salt to taste. Mix well and set aside.
After the dough has rested, divide it into 6 equal portions. Roll each portion into a ball and flatten it slightly.
Place a spoonful of the onion filling in the center of each flattened dough ball. Bring the edges together and seal the filling inside. Gently flatten the stuffed dough balls again.
Heat a tawa or non-stick pan over medium heat. Roll out each stuffed dough ball into a 5-6 inch circle, taking care not to let the filling spill out.
Place the rolled-out kulcha on the hot tawa and cook for 1-2 minutes on each side, or until golden brown and slightly puffed. Apply a little oil or ghee on both sides while cooking.
Serve the onion kulche hot with a side of yogurt, pickle, or your favorite curry.