Heat oil in a heavy-bottomed pan over medium heat.
Add fennel seeds and let them sizzle for 30 seconds until fragrant.
Add finely chopped onion and garlic-ginger paste; sauté for 3-4 minutes until onion is translucent.
Add chopped hot peppers and fry for 2-3 minutes, stirring carefully.
Stir in tomato paste, chili powder, kasuri methi, chilli flakes, and salt to taste.
Cook for 8-10 minutes, stirring frequently, until oil begins to separate from the mixture.
Add garam masala and fresh coriander; mix well and cook for another 2 minutes.
Remove from heat and let cool slightly before using.