Preheat the oven to 400°F (200°C). In a mixing bowl, combine ground beef, bread crumbs, egg, garlic, oregano, salt, and pepper. Mix until well combined.

Form the mixture into meatballs, about 1 inch in diameter, and place them on a baking sheet.

Bake in the preheated oven for 20-25 minutes or until cooked through.

In a bowl, combine Greek yogurt, grated cucumber, garlic, olive oil, lemon juice, dill, and salt. Mix well and refrigerate until ready to use.

In a pot, melt butter over medium heat. Add rice and toast for 2-3 minutes.

Add chicken broth, lemon juice, and salt. Bring to a boil, then reduce heat to low, cover, and simmer for 15-20 minutes or until rice is tender.

In a bowl, combine sliced cucumber, cherry tomatoes, red onion, olive oil, red wine vinegar, salt, and pepper. Toss to combine and set aside.

In serving bowls, layer lemon rice, meatballs, tzatziki sauce, and cucumber salad. Serve immediately.