Based on sweet, fresh corn, this salad says summer. If the corn is very moist and sweet, use it raw. If not, blanch the kernels in boiling water for 1 minute. Drain and refresh them in cold water to stop the cooking. The salad will hold up for hours and is best at room temp.
Heat 2 Tbs. oil in skillet over medium heat, and cook onion 2 to 3 minutes. Add chili powder and cumin, and cook 1 minute more. Cool in bowl. Add corn, peppers and tomatoes to onion. Fold in cilantro.
Whisk together remaining 4 Tbs. oil and vinegar, drizzle over salad and toss to combine well. Season to taste with salt and pepper, and serve.