Prepare the Tzatziki: In a medium-sized bowl, combine 1 cup Greek yogurt, 1/2 grated cucumber, 2 cloves minced garlic, 1 tbsp chopped dill, and 1 tbsp lemon juice. Season with salt and pepper to taste. Mix until well combined, cover, and refrigerate for at least 30 minutes to let the flavors meld.
Make the Meatballs: Preheat your oven to 400°F (200°C). In a large mixing bowl, combine the 1 lb ground chicken, 1/2 cup whole wheat breadcrumbs, 1/4 cup grated Parmesan, 1/4 cup chopped parsley, 1/4 cup chopped red onion, 2 cloves minced garlic, 1 large egg, 1 tsp dried oregano, 1 tsp salt, 1/2 tsp black pepper, and 1/2 tsp ground cumin.
Mix gently with your hands until all ingredients are thoroughly combined, but be careful not to overmix, as this can make the meatballs tough. Form the mixture into 1-inch balls.
Arrange and Bake: Place the meatballs on a lined baking sheet. Drizzle with 1 tbsp olive oil to help them crisp up as they cook. Bake in the preheated oven for 20-25 minutes or until the meatballs are golden brown and cooked through.
Serve: Once cooked, remove the meatballs from the oven and allow them to cool slightly. Serve warm with the tzatziki sauce on the side. These meatballs are perfect on their own, served in pita bread, or even crumbled atop a fresh salad!