Greek Turkey Burgers with Tzatziki Sauce

For the Turkey Burgers

ground turkey

fresh spinach leaves, chopped

sun-dried tomatoes, chopped

red onion, minced

feta cheese, crumbled

garlic, pressed or minced

egg, whisked

olive oil

dried oregano

each Kosher salt and freshly ground black pepper

soft whole-wheat hamburger buns

Bibb lettuce leaves

Sliced red oinon

For the Tzatziki Sauce

cucumber, halved with skin and seeds removed

low-fat plain Greek yogurt

garlic, pressed or minced

red wine vinegar

fresh dill, minced

kosher salt and freshly ground black pepper