First, measure all taco seasoning spices into a jar, seal with a lid, and shake well to combine. You’ll end up with approximately 1 cup of taco seasoning, which can be stored in your cupboard for later use.
In a large, heavy saucepan, heat the oil over medium heat. Add the chopped onion and garlic; sauté until the onion softens and begins to turn golden, about 5 minutes. Stir in 2 Tbs. of the homemade taco seasoning and 1 tsp. of kosher salt, and cook for another 30 seconds.
Add the lentils and chicken or vegetable broth to the pot and raise the heat to high. Bring to a boil and then lower to a simmer. Cover the pot with a lid and simmer for about 25 minutes, stirring occasionally. Remove the lid and allow the last bit of the liquid to cook out, stirring.
Serve spiced lentils with crunchy taco shells, shredded lettuce, grated cheese, diced tomato, sour cream, pickled jalapeños, salsa, and any other classic toppings your heart may crave.