Heat vegetable oil in a large pot over medium heat. Stir in onion, salt, and black pepper; cook and stir until onion has softened and turned a light golden brown, about 10 minutes.
Add lamb, cinnamon, cumin, coriander, and garlic paste. Cook on medium heat, stirring occasionally, until lamb starts to brown, 10 to 15 minutes. Stir in tomatoes and tomato paste; cook and stir for another 5 minutes.
Dissolve beef bouillon cubes in 4 cups boiling water. Pour broth into the pot with lamb and stir in okra. If necessary, add water to cover okra. Cover and simmer for 30 minutes, stirring occasionally.
Remove the cover and cook until lamb is very tender and stew reaches desired thickness, 45 minutes to 1 hour