Adapted from Emily Connor, Food52.
Heat 2 tablespoons of the extra virgin olive oil in a medium saucepan. When it is hot, add the farro and stir to toast the grains. Cook, stirring occasionally, for 3-5 minutes until fragrant.
Cover the farro with water by at least 2 inches. Bring to a boil. Let simmer for 15 minutes and then add a generous pinch of salt. Let continue cooking until the farro is cooked to taste, which for me is chewy-tender. It should take around 25 minutes total. Drain the farro when it is done and leave to cool a bit.
While the farro is cooking, make sure all of your veggies are prepped.
Heat 1 tablespoon of the oil with the butter in a large skillet. When it is hot, add the onion with a pinch of salt. Cook for 7 minutes, stirring occasionally, and add the garlic. Cook another 2-3 minutes, stirring.
Add another tablespoon of oil. Add the Aleppo pepper flakes and let them roast for a minute. Then add the asparagus spears and stir briefly. Then add the asparagus "coins" and continue cooking. Sauté until the asparagus is tender-crisp, another few minutes.
Add the drained farro to the asparagus-onion mixture (right in the pan is fine). Turn the heat off and add the remaining extra virgin olive oil, lemon zest, lemon juice and lemon vinegar. Toss to evenly coat with all ingredients. Add a turn or 2 of freshly ground black pepper.
Taste for more extra virgin olive oil, salt, black pepper, lemon juice or lemon vinegar.
Remove the salad to a bowl to cool further, about 10 minutes. Mix in the chopped pistachios and tarragon. Garnish with feta cheese. The salad can be served immediately or it can cool to room temperature. We still enjoyed the leftovers the next day after chilling.