In a large mixing bowl, combine 200 grams of all-purpose flour (maida) and a pinch of salt. Gradually add water and knead the mixture into a smooth, soft dough. Cover the dough with a damp cloth and let it rest for 30 minutes.
In another bowl, mix 200 grams of grated cheese (preferably mozzarella or cheddar), 1 finely chopped onion, 1/2 teaspoon of black pepper powder, and salt to taste.
Divide the dough into small equal-sized balls. Roll out each ball into a thin, circular shape using a rolling pin.
Place a spoonful of the cheese mixture in the center of each dough circle. Fold the dough over the filling, forming a half-moon shape, and seal the edges by pinching them together.
Heat oil in a deep frying pan or kadai over medium heat. Once the oil is hot, carefully slide the momos into the oil and fry them until they turn golden brown and crispy. Make sure not to overcrowd the pan.
Use a slotted spoon to remove the fried momos from the oil and place them on a plate lined with paper towels to absorb excess oil.
Serve the cheese fried momos hot with tomato ketchup or spicy chutney.