Tacos de frijoles con queso are traditional Mexican tacos that can be found throughout the country. They're usually made by topping small corn tortillas with a combination of chili peppers (often of the ancho variety), onions, garlic, beans, and cumin.
The onions, garlic, chili peppers, and cumin are cooked in a skillet, then mixed with the mashed beans. The tortillas are fried in a bit of oil on both sides until crispy, then filled with the beans and garnished with shredded lettuce and grated cheese, most commonly of the cotija variety.