1. In a large bowl, stir together the vinegar and salt. Add broccoli and toss to combine.
2. In a large skillet, heat olive oil until hot, but not smoking. Add garlic and cumin and cook until fragrant, about 1 minute. Stir in sesame oil and pepper flakes. Pour mixture over broccoli and toss well. Let sit for at least 1 hour at room temperature, and up to 48 (chill it if you want to keep it for more than 2 hours). Adjust seasonings (it may need more salt) and serve.