Meanwhile, toss sweet potato, onion, zucchini, and squash with oil, salt, and black pepper. Remove the baking sheet from the oven and coat generously with non-stick cooking spray. Spread vegetables out evenly onto the prepared baking sheet. Roast, stirring once halfway through cooking time, until vegetables are fork-tender, about 30 minutes. Remove baking sheet from the oven, add the kidney beans, and stir to combine. Return the baking sheet to the oven and cook for an additional 5 minutes.
For the Dressing:
4 Add the yogurt, buttermilk, garlic, chives, parsley, spinach, tarragon, and salt to the bowl of a small food processor. Blend, scraping down the sides as needed, until smooth. Transfer to a bowl then cover and refrigerate until ready to use.
For the Eggs:
5 Bring a small saucepan of water to a simmer over medium-high heat. Use a spoon to gently drop eggs into water; cook for 8 minutes. Drain carefully using a slotted spoon and place eggs in an ice bath to stop the cooking process. Once cooled, peel and slice the eggs in half.
For the Bowls:
6 To serve, drizzle farro and spinach among serving bowls. Toss vegetables and beans with 1 tablespoon dressing and distribute among bowls. Top with eggs and drizzle bowls with remaining dressing.