Recipe: Greek beef pitas with easy tzatziki

Ingredients

• ¼ English cucumber, seeded
• 1 cup 2% Greek yogurt or sour cream
• 4¼ tsp garlic powder, divided
• 4 tbsp freshly squeezed lemon juice, divided
• 1 tsp extra-virgin olive oil
• 1 lb lean ground beef
• ½ red onion, chopped
• 2 tsp dried oregano
• 2 tsp lemon zest
• ½ tsp each: salt and freshly ground black pepper
• ½ cup chopped fresh parsley or mint
• 4 Greek-style pitas, lightly toasted
• 2 cups packed baby spinach or baby kale
• 16 cherry tomatoes, halved