Mix the red onion, yellow pepper, juice of 1 lime and 2 Tablespoons of the rice vinegar with the halibut slices and refrigerate 4-6 hours (or overnight). Drain any liquid. Separately, mix the juice and zest of one lime, 1 tablespoon of rice vinegar, the olive oil, cilantro and chili flakes. Mix dressing with halibut when ready to serve.