First, dice all the veggies and rinse the lentils to remove any debris. Then, add the veggie broth, lentils, and ½ tablespoon of the taco seasoning to a small saucepan. Cook the lentils uncovered for 25-30 minutes until they are soft. Check and stir periodically to make sure the lentils are not getting overcooked. Start with 1 ¼ cup vegetable broth and add up to ¼ cup more broth if the lentils are sticking to the pan before cooked through. The lentils are done when they are slightly crunchy on the outside(not mushy!), soft and tender inside, and no liquid is left in the pan. As a final step, season the cooked lentils with salt and pepper to taste.
While the lentils are cooking, add 1 tablespoon of oil to a large pan or cast iron skillet and turn the heat on. Once the oil is hot, add in the chopped onion, garlic, red/green pepper, and 1 tablespoon of taco seasoning. Saute for 5 minutes until the vegetables are cooked, but still crispy. Then, turn off the heat and season with salt and pepper to taste.
Add the cooked lentils to the skillet with vegetables and 1 teaspoon of lime juice. Stir to mix everything together. Then, fill each taco shell with 1 scoop of the lentil taco filling!