In a large, heavy-bottomed pot, heat the lard or oil over high heat.
Once hot, add the ground meat and cook, stirring occasionally, until well browned, about 10 minutes.
Add the salt, pepper, onion, cumin, oregano, chile, and cinnamon, and cook, stirring frequently, until the onion is tender and the spices are fragrant, about 4 more minutes.
Add the canned tomatoes, potato, and 1 cup water.
Bring to a boil, lower to a simmer, and cook until the potato is very tender and the picadillo is reduced and thickened, about 20 minutes.
Serve in crisp tortilla shells with cheese (place the cheese on the bottom, followed by the hot picadillo, so the cheese melts and glues the taco together), lettuce, tomato, avocado, and salsa.