In a large saucepan, melt butter over medium heat. Add onion and cook, stirring occasionally, for 5 minutes or until translucent. Add rice and garlic; cook, stirring, about 5 minutes or until rice is hot. Increase heat to medium-high. Add wine; stir until wine is absorbed. Add chicken broth, 1 cup at a time, stirring frequently and letting each addition be absorbed before adding the next addition. When rice is tender and creamy, stir in arugula, radicchio, dried plums, grated cheese and lemon zest; season with salt and pepper. Portion into 6 shallow bowls and garnish with shaved Parmesan cheese.