Make Cilantro-Pepper Vinaigrette: combine first 6 ingredients in small bowl. Let stand at room temperature until ready to serve.
Heat 1 T. vegetable oil in medium skillet over medium heat. Add onion, bell pepper, corn, and garlic and cook, stirring occasionally, about 5 minutes. Let cool slightly.
Combine salmon, bread crumbs, cilantro, lime juice, egg, salt, cayenne, and vegetables. Shape into 8 cakes, about 2-1/2 inches wide, then coat with cornmeal, shaking off excess.
Heat 1 T. each oil and buter in heavy medium skillet over medium heat. Place 4 cakes in skillet and cook, turning once, until golden brown, 6-8 minutes. Keep warm in oven. Repet with remaining cakes. Serve hot with vinaigrette.