Start by making the spicy black beans. Heat skillet to a medium heat and add oil to the heated pan. Rotate pan to spread the oil and add minced garlic.
Set aside 2 Tablespoons of the raw red onions to use as a topping. Sauté remaining onions with garlic in pan until fragrant and translucent, about 3 minutes.
Add black beans, cumin, ancho chili powder, oregano, coriander, paprika, lime juice, and water to the pan. Use a spatula to fully combine the beans and spices.
Once the black bean mixture has warmed and any excess liquid has cooked off, add salt to taste.
Put the corn taco shells in the oven and warm them for 5 minutes. Or warm them in the air fryer. Tuck the corn shells inside of each other, then put them into the air fryer basket. Heat at 370 degrees for 3 to 4 minutes. Be careful removing them from the air fryer basket. They will be hot.
Stuff the corn shells with a spoonful of spicy black bean mixture, chopped tomato, romaine lettuce, red onion, and guacamole.
These tacos are also delicious topped with shredded non-dairy cheddar cheese. I'm especially a fan of Daiya homestyle cheddar block, grated by hand.