In a medium saucepan, bring the vegetable broth to a boil. Add the lentils, reduce heat, cover, and simmer for 12–15 minutes, or until just tender and the liquid is absorbed.
While the lentils cook, dice the sweet potatoes into ½-inch cubes. Mince the garlic and jalapeño (remove seeds for less heat).
In a large skillet, heat 2 tablespoons of oil over medium heat. Add the diced sweet potatoes and cook, stirring regularly, for about 10 minutes or until fork-tender and lightly browned.
Add the garlic, jalapeño, paprika, oregano, cumin, and salt to the skillet. Stir for 3–5 minutes until fragrant.
Add the cooked lentils and stir well to combine. If the mixture looks dry, add 2–3 tablespoons of water or broth. Remove from heat and squeeze lime juice over the mixture to finish.
Slice the avocados and chop the green onions and cilantro (if using).
Heat 1 tablespoon of oil in a skillet over medium-low heat. Working in batches, toast the tortillas for about 1 minute per side until slightly crisp and browned in spots. Add more oil as needed between batches.
Spoon 2–3 tablespoons of the sweet potato-lentil mixture into each tortilla. Top with avocado, green onion, and cilantro. Serve warm.