Arrange the walnuts on a sheet pan and cook until aromatic and lightly toasted, about 8 minutes. Set aside.
In a medium saucepan, combine 2 cups waters, the quinoa, and a pinch of salt. Bring to a boil over high heat and then reduce the heat to low to maintain a gentle simmer. Cook, partially covered, until the quinoa pops open and becomes tender, about 15 minutes. Remove from the heat, sprinkle the dried cherries on top of the quinoa, cover, and set aside while you make the vinaigrette.
Meanwhile, in a large bowl, whisk together the olive oil, vinegar, mustard, and honey. Season with a pinch of salt and a twist of black pepper. Add the onion, toss to combine, and set aside for 5 minutes.
Add the quinoa, kale, spinach, and garlic to the dressing and toss to combine. Taste and adjust for seasoning, adding salt and pepper as needed.