In a large non-stick skillet, heat oil over medium heat. Sauté onion and garlic until tender. Add lentils and spices. Cook for 1 minute.
Stir in broth and bring to a boil. Reduce temperature and simmer, covered, until lentils are tender. From 25 to 30 minutes.
Cook uncovered until mixture thickens (6 to 8 minutes), stirring occasionally. Lightly crush the lentils, stir in the salsa and heat through. Serve in taco shells, covering with remaining ingredients.