In a blender, combine vinegar, shallot, mustard, 1 tablespoon water, 3 tablespoons of the almonds and 1/4 cup of the pitted cherries. Blend until very smooth, about 1 minute. Stir in tarragon.
Combine arugula, cooked grains and remaining cherries in a large bowl. Toss with the dressing and garnish with the remaining 3 tablespoons almonds.