Japanese Curry

Name: Japanese Curry
Ingredients: 1 tablespoon vegetable oil, or more as needed; 1.75 pounds beef chuck, cut into 2-inch cubes; 3 onions, quartered; 1 tablespoon ketchup; 1.5 teaspoons Worcestershire sauce; 1 pinch cayenne pepper, or to taste; water to cover; 4 carrots, cut into 2-inch pieces; 1 cube chicken bouillon; 3 medium potatoes, cut into 3-inch chunks; 1.5 (3.5 ounce) containers Japanese curry roux, or more to taste