In a medium bowl, whisk chickpea flour, turmeric, cumin, chile powder, salt, and black pepper to combine.
Add water, whisking until batter is smooth and pourable. (A few small lumps are OK. Batter should resemble a loose pancake or crêpe batter; if batter is too thick, add water, 1 tablespoon at a time, until batter is the right consistency.)
Using a flexible spatula, fold in ginger, onion, tomato, and cilantro to combine.
In an 8-inch cast iron, carbon steel, or nonstick skillet, heat 1 teaspoon oil over medium-high until just shimmering.
Using a ¼ cup measuring cup, scoop batter onto skillet and, using a flexible spatula, spread batter into a circle 5- to 6-inches in diameter.
Cook until edges are crispy and bottom is golden brown, about 2 minutes.
Carefully flip chilla and cook until bottoms are lightly golden and cooked through, 1 to 2 minutes.
Transfer to a large plate and repeat with remaining batter.
Serve hot with green chutney, aachar, and/or ketchup. Season to taste with additional salt and pepper as needed.