How to Make It
Stir together ground meat, 1/2 teaspoon salt, and 1/2 teaspoon pepper in a bowl; shape into 12 meatballs. Heat 1 tablespoon oil in a nonstick skillet over medium-high. Add meatballs; cook until browned on all sides, about 12 minutes. Remove from heat.
Whisk together lemon juice, remaining 3 tablespoons oil, remaining 1/2 teaspoon salt, and remaining 1/2 teaspoon pepper in a small bowl. Stir together yogurt, 1 tablespoon water, chives, dill, and lemon zest in a separate small bowl.
Toss together arugula and 2 tablespoons oil mixture in a large bowl; place 1 cup mixture on each of 4 plates. Toss together tomato slices and 2 tablespoons oil mixture in the same bowl; add 1/2 cup tomatoes to each plate. Gently toss avocado slices with remaining 1 tablespoon oil mixture in bowl; divide evenly among plates. Place 3 meatballs on each plate; drizzle each with 1 tablespoon yogurt mixture.