.Combine fish sauce and 1/2 cup red onions in a shallow dish. Add the steak, turning to coat. Let stand at room temperature for 1 hour, turning after 30 minutes.

Meanwhile, course chop 1 bell pepper. Place in a saucepan with 1 cup water and 1/4 cup onions. Bring to a boil, then reduce heat and cook over medium heat 10 minutes, until the peppers and onions are tender. Drain and transfer to a food processor or blender and process until smooth. Stir in 1 tablespoon of the oil and salt.

Slice remaining bell pepper. Heat a large skillet over high heat. Swirl 1 TBSP oil in pan. Add slice bell pepper, corn and remaining onions. Cook 15 minutes until peppers are wilted and corn is lightly charred, stirring occasionally. Salt and pepper to taste, remove from pan and keep warm.

Remove steak from marinade and discard marinade.Return skillet to high heat and add steak to pan,