Heat the vegetable oil in a large pot over medium heat. Add the lamb cubes and brown them on all sides for even flavor.
Add the diced onion, minced garlic, and grated ginger to the pot. Cook until the onion softens and turns translucent.
Stir in the curry powder and ground cumin. Cook for one minute to release the spices.
Pour in the diced tomatoes, rinsed lentils, and vegetable broth. Bring the mixture to a boil, then reduce to a simmer.
Cover and cook for 45 minutes, stirring occasionally, until the lamb is tender and the lentils are soft.
Add the fresh spinach and stir until it wilts into the stew. Season with salt and black pepper to taste.
Ladle into bowls and top with chopped cilantro before serving.