Prepare the marinade by mixing olive oil, soy sauce, lime juice, crushed garlic, red pepper flakes, ground cumin, and brown sugar in a bowl.
Place the skirt steak or chicken breasts in a shallow dish and pour the marinade over the meat.
Cover and refrigerate for at least 2 hours.
Slice the onion and bell peppers into thin strips. Set them aside.
Heat a large skillet over medium heat, add a bit of oil, and sear the marinated meat for about 7-8 minutes per side or until cooked through.
In the same skillet, sauté the onion and bell peppers until tender.
Add the cooked meat back to the skillet and mix everything together.