Return the skillet to medium-high heat and add the oil. When the oil is hot, add the onion, garlic and ginger. Season with salt. Cook until softened, 5 minutes. Add the tomato, garam masala, cumin, coriander and jalapeño, and cook until fragrant and the tomato begins to break down, 3 to 5 minutes more. Remove from the heat and transfer to a large bowl.