In a large skillet, heat the oil until smoky. Add the chile and onion and stir-fry over high heat for 30 seconds. Add the garam masala and stir-fry until the onion is crisp-tender, 2 minutes. Toss in the tomatoes and lime juice. Transfer to a bowl; season with salt and pepper. Stir in the cilantro. Serve hot or at room temperature.