In a 10-inch nonstick skillet, heat oil over medium-high heat, until shimmering. Add onions and stir until softened, about 1 minute. Add tomatoes, mix well, and cook until most of the excess moisture has evaporates, about 1 minute.
Add green chillies and ginger-garlic paste, and stir until fragrant, about 30 seconds. Add red chili powder and turmeric powder, and stir until oil separates from the paste, about 30 seconds, taking care not to burn the paste.
Turn the heat to low. Add eggs and salt, and gently stir until the mixture begins to form soft curds, about 1 minute. Increase the heat to high, and vigorously stir the mixture, breaking bigger clumps of egg apart. Add 1 teaspoon of butter, and stir until melted. Stir in half of the cilantro. Remove from heat, and serve immediately, garnishing with remaining coriander and a teaspoon of butter. Serve with lightly toasted bread.