Spring Vegetable Sauté

Name: Spring Vegetable Sauté
Ingredients: 3 Tbsp. unsalted butter, divided; 1 lb. medium-sized rainbow carrots, peeled, halved lengthwise, and cut on a bias into 2-in. pieces (2 1/2 cups); 8 oz. multicolored radishes, trimmed and halved (if small) or quartered (if large) (1 1/2 cups); 2 tsp. granulated sugar; 3/4 tsp. kosher salt; 1/4 tsp. black pepper; 1 cup fresh snow peas, trimmed and cut in half diagonally (about 4 oz.); 1 cup frozen sweet peas; 2 tsp. fresh lemon juice (from 1 lemon); 2 Tbsp. finely chopped fresh chives, plus more for garnish