Add udon noodles to a large pot of water and cook according to package directions, or until tender. Drain and rinse noodles under cold running water. Set aside to drain well.
Warm oil in a large skillet over medium heat. Add peppers and sauté for about 10 minutes. Stir in salt, reduce heat to low, cover skillet, and cook for 5 minutes.
Remove lid and raise heat to medium. Cook, stirring constantly, for 5 more minutes or until peppers are cooked through and begin to brown. Stir in chili flakes and set aside to cool.
Add garlic, tamari, rice vinegar, and sesame seeds to a small bowl. Whisk to combine. Drizzle in sesame oil and whisk again.
Place noodles and half of the marinade in a large salad bowl. Toss until evenly coated. Add extra marinade as desired.
Cut corn off cobs and add to noodles along with scallions and cilantro. Mix well to combine, then gently stir in peppers. Season to taste with extra tamari or kosher salt.
Sprinkle with black sesame seeds and serve at room temperature.