Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper for easier cleanup.
In a large mixing bowl, combine the ground turkey, breadcrumbs, onion, garlic, parsley, oregano, cumin, salt, pepper, and beaten egg. Mix until well combined.
Form the mixture into meatballs, about 1 to 1.5 inches in diameter, and place them on the prepared baking sheet.
Drizzle olive oil over the meatballs to help them brown. Bake in the preheated oven for 20-25 minutes, or until they are cooked through and golden brown.
While the meatballs are baking, prepare the Tzatziki sauce. In a bowl, mix the Greek yogurt, grated cucumber, garlic, olive oil, dill, lemon juice, and season with salt and pepper to taste. Stir until all ingredients are well combined.
Once the meatballs are done, remove them from the oven and let them cool slightly. Serve warm with the Tzatziki sauce on the side.