Ingredients

Nonstick olive-oil cooking spray
4 6-inch whole-wheat hoagie rolls, split; 8 slices whole-wheat bread; or 2 whole-wheat pita bread rounds, halved crosswise and split horizontally
4 cups fresh baby-spinach leaves
8 thin tomato slices (1 medium tomato)
1/4 teaspoon kosher salt
1/8 teaspoon freshly ground black pepper
1/4 cup thinly sliced red onion
2 tablespoons shredded fresh basil leaves
1/2 cup crumbled feta cheese (2 ounces)