Preheat oven to 400°F (200°C).
In a mixing bowl, combine ground lamb, beaten egg, breadcrumbs, minced garlic, ground cumin, ground coriander, salt, and black pepper. Mix well.
Form the mixture into meatballs and place on a baking sheet. Bake for 20 minutes or until cooked through.
While the meatballs are baking, heat olive oil in a saucepan over medium heat. Add chopped onion and minced garlic, and sauté until softened.
Add crushed tomatoes, ground cumin, ground coriander, salt, and black pepper to the saucepan. Simmer for 10 minutes.
Once the meatballs are done, add them to the sauce and simmer for another 5 minutes. Serve hot.