Combine the taco seasoning, oregano, cumin, and coriander in a small bowl and stir to combine. Set aside.
Make the taco filling
Fill a cup with water and place next to the stove to add to the pan as you cook. Preheat a large skillet over medium-high heat and add the oil. Saute the onion, garlic, and a pinch of salt for about 3 minutes, until lightly browned. Add the spice blend and toss for 30 seconds to toast the spices.
Lower the heat to medium, and add the lentils along with a few splashes of water, the tomato paste, and hot sauce. Use the back of a wooden spoon, a spatula, or a fork to mash the lentils as they cook until they hold together. Continue mashing and stirring the lentil mixture for approximately 5 minutes, adding small splashes of water as necessary when the lentils look like they are drying out.
Stuff the tacos
Preheat the oven to 400°F. Arrange the taco shells standing up in a 11 x 7 x 2-inch pan. Divide the lentil mixture among the taco shells and divide the cheese among the tacos as well. Bake for 10-15 minutes until the taco shells are beginning to brown and the cheese is melted.
Top each taco with salsa, shredded lettuce, cherry tomatoes, cilantro, avocado, pepitas, and roasted poblano cashew cream or sour cream.