In a small bowl, dissolve cornstarch in 2 tablespoons of boiling water. Set aside.
Heat oil in a heavy bottomed pot over high heat. Add sliced onions. Sauté for about 5 minutes or until onions are soft and translucent.
Add beef chunks. Sear the meat and keep on stirring until brown on all sides.
Season with salt, cumin, dried oregano and paprika.
Add diced squash, potatoes, carrots, bell pepper, corn on the cob and tomato sauce.
Stir in cornstarch slurry and boiling water to the mixture. Cover pot, reduce the heat and let the mixture simmer until beef is tender. Stir frequently.
Adjust seasonings according to your taste.
Garnish with chopped fresh cilantro just before serving.