Preheat the oven to 400°F. Line a baking sheet with parchment paper.
In a large bowl, combine ground turkey, breadcrumbs, Parmesan cheese, parsley, onion, garlic, egg, oregano, salt, black pepper, and red pepper flakes. Mix until well combined.
Form the mixture into meatballs, about 1.5 inches in diameter, and place them on the prepared baking sheet.
Bake in the preheated oven for 20-25 minutes, or until the meatballs are cooked through and golden brown.
While the meatballs are baking, prepare the tzatziki sauce. In a medium bowl, mix together Greek yogurt, grated cucumber, garlic, lemon juice, olive oil, dill, salt, and pepper. Adjust seasoning to taste.
Once the meatballs are done, serve them warm with a generous dollop of tzatziki sauce on the side.