Slow-Cooker Pork Pita Sandwiches with Tzatziki

Pork

• 1 large yellow onion, cut into wedges
• 3 lb boneless pork shoulder, trimmed of all visible fat
• 2 tablespoons fresh lemon juice
• 2 tablespoons chopped fresh or 2 teaspoons dried oregano leaves
• 3/4 teaspoon coarse ground black pepper
• 1/2 teaspoon salt
• 3 large cloves garlic, finely chopped (3 teaspoons)
• 1/2 teaspoon salt

Tzatziki

• 1 1/2 cups plain nonfat Greek yogurt
• 1 English (hothouse) cucumber, peeled, seeded, diced (1 1/2 cups)
• 1 tablespoon lemon juice
• 1/2 teaspoon salt

Pocket Flatbreads and Fillings

• 6 whole wheat thin pocket flatbreads (7 inch), cut in half
• 2 cups baby spinach
• 6 plum (Roma) tomatoes, cut into 6 slices each
• 12 lemon wedges, if desired