On a foil lined add the butternut squash and toss with 1 tablespoon of the olive oil, salt, and pepper. Bake for 40 minutes. After 20 minutes rotate the butternut squash to let all sides cook evenly.
Remove from oven and set aside.
Cooking the Farro
While the squash is roasting, rinse farro and bring a pot with 2 cups of water to a boil, add the farro and 1 tsp of salt, reduce heat to low and cover. Let the farro simmer for 20-30 minutes or until farro has expanded.
Remove from heat, fluff with a fork, and set aside.
Caramelizing the onions
In a sauté pan on medium high heat, heat the butter until it has melted. Add the onions and cook until they start to turn translucent. Reduce the heat to medium low and cover. Allow to cook stirring occasionally until the have released their liquid, about 20 min.
Blistering the tomatoes
In a sauté pan, on medium high heat, add 1 tbsp of olive oil and add the cherry tomatoes. Sauté the tomatoes undisturbed for 2 minutes and then gently stir to rotate the sides that touch the bottom of the pan. Let cook undisturbed again for 2 minutes before gently stirring again. Repeat this process until most of the tomatoes have split skin. Remove from the heat and set aside.
Heat a medium skillet over medium/high heat. Add olive oil. When olive oil is fragrant add sage and sauté for 1-2 minutes.
Turn heat to low heat and simmer for 5-10 minutes. Then remove from heat and let cool. In a bowl or jar whisk/mix the remaining ingredients
Assemble the Salad
In a large bowl add the farro, brussels sprouts, and arugula. Drizzle in about 1/3 of the dressing and toss. This will make tossing the rest of the salad easier. Add the rest of the rest of the salad ingredients and drizzle the remaining dressing on top. Toss to evenly coat and mix.