In a small sauté pan, warm olive oil over medium heat. Add onion and sauté a few minutes. Add chili powder and cumin and sauté 1 minute longer. In a serving bowl, combine corn, bell peppers, tomatoes and cooled onions. Toss to mix. Add cilantro and vinegar. Toss well to combine. Season to taste with salt and pepper and toss again. This recipe is best served at room temp.