Cut off both ends, then slice lengthwise into 4 strips (faster cooking, better texture than rounds).
2. Temper
Heat oil in a wide pan or wok over medium-high. Add mustard seeds — when they pop, add cumin seeds. Then add green chilies and onion. Sauté until onion is golden, ~5 min.
3. Add garlic + spices
Add garlic, cook 1 min. Add turmeric, coriander powder, chili powder, and salt. Stir 30 seconds.
4. Cook the tindora
Add tindora, toss well to coat in the masala. Cover and cook on medium for 12–15 min, stirring every few minutes.
5. Finish
Uncover, turn heat to high, stir-fry 3–4 min to evaporate moisture and get a little char on the edges. Add garam masala, toss, top with cilantro. Serve with roti or as a side.
Tips
Pick firm, bright green tindora with no yellowing — yellow ones can be bitter
South Indian version: skip the onion, add curry leaves and a handful of fresh/frozen coconut at the end