Rinse the farro thoroughly under cold water then add the farro to a medium saucepan with the 3 cups of water and bring to a boil.
Reduce the heat to medium-low and simmer, stirring occasionally, for 30 minutes. Drain farro of any excess liquid and set aside.
Heat the oil in a large skillet over medium heat. Add the onion and cook, stirring occasionally, until softened, about 8 minutes.
Add the cooked farro to the pan along with the paprika, cumin, garlic, oregano, 1/2 tsp salt, and the 1/4 cup water. Stir to combine and cook until heated through, about 2 minutes
Season with salt and pepper to taste.
Warm up your taco shells and fill with the farro mixture and your favorite toppings.