Place the lentils in a medium pot and cover with 3 cups of water. Bring to a boil, then reduce to a simmer and cook for 20 minutes until tender. Drain any remaining liquid and set the lentils aside.
Heat the vegetable oil in a large skillet over medium heat. Add the diced onion and cook for 3 minutes until it starts to soften.
Stir in the minced garlic, diced potatoes, cumin, chili powder, smoked paprika, and salt. Cook for 10 minutes, stirring often, until the potatoes are tender and lightly browned at the edges.
Add the cooked lentils to the skillet and stir everything together. Cook for another 3 minutes so the flavors combine.
Warm the corn tortillas in a dry skillet or over a low flame for 20 seconds on each side.
Spoon the lentil and potato mixture into the tortillas. Top with chopped cilantro and serve with lime wedges on the side.