In a bowl, whisk together lemon zest, lemon juice, honey, garlic, and red pepper flakes. Slowly stream in the olive oil from the jar of sun-dried tomatoes along with extra olive oil until smooth. Chop the sun-dried tomatoes and stir them in with fresh herbs and salt to taste.
Bring a large pot of salted water to a boil and add the rinsed farro. Simmer until tender but still slightly chewy, about 25 minutes. Drain well and spread it onto a sheet pan so it cools quickly and doesn’t become mushy.
Heat olive oil in a skillet over medium heat and toast the walnuts until fragrant. Remove them and set aside. In the same pan, sauté diced fennel until softened and lightly golden, which enhances its natural sweetness.
In a large bowl, combine cooled farro, walnuts, fennel, arugula, mozzarella, olives, artichokes, sopressata, and peppers. Pour half of the vinaigrette over the mixture and gently toss to coat. Transfer to a serving platter and drizzle the remaining dressing over the top.