Slice finely the onion and place it in a bowl of ice-cold water to let it soak for 10-15 minutes. Thus, we leach out some of its "bite." Then, completely drain them from the water and add to the bowl with the carrots;
Combine vinegar, chile, soy sauce, olive oil, minced garlic, and black pepper in a small bowl;
Pour dressing over carrots and onions. Toss carrots and onions with the sauce in a bowl. Taste and adjust seasoning if needed;
Serve the salad in a shallow serving bowl, garnished with toasted sesame seeds.