greek lamb burgers w/ spinach & red onion salad

Ingredients

• 1/3 cup chopped fresh mint
• 2 teaspoons paprika
• 3/4 teaspoon ground cinnamon
• 1/2 teaspoon salt
• 3 tablespoons olive oil, divided
• 1 1/3 pounds ground lamb
• 4 - hamburger buns or small ciabatta rolls
• 1 1/2 cups baby spinach leaves
• 1 1/3 cups crumbled feta cheese
• 4 - red onion slices, 1/4-inch thick
• 1 1/2 teaspoons balsamic vinegar