Meanwhile, peel, halve, and thinly slice onion; transfer to a baking sheet pan.
1 medium red onion
Wash, dry, seed, and medium dice bell peppers; add to the baking sheet.
2 yellow bell peppers
Drizzle veggies with oil and season with salt and pepper; toss to combine and spread out in an even layer. Place veggies in the oven and bake until tender, 12-15 minutes.
4 tsp extra virgin olive oil
½ tsp salt
¼ tsp black pepper
Meanwhile, peel and mince garlic.
4 cloves garlic
Preheat a large skillet over medium heat.
While the skillet heats up, pat chicken dry with paper towels and small dice.
1 ½ lb chicken breasts, boneless skinless
Once the skillet is hot, add oil and swirl to coat the bottom. Add garlic and chicken to the skillet and sauté until golden brown and cooked through, 8-10 minutes.
2 tsp extra virgin olive oil
While the chicken is cooking, place tomato sauce, ketchup, Dijon, sugar, vinegar, Worcestershire, and spices in a medium bowl. Whisk to combine.
1 (8 oz) can tomato sauce
2 tbsp ketchup
2 tbsp Dijon mustard
4 tsp brown sugar
4 tsp apple cider vinegar
4 tsp Worcestershire sauce
1 tsp salt
1 tsp onion powder
½ tsp chili powder
Pour sauce into the skillet with the chicken. (Reserve bowl for later use). Stir and bring to a simmer over high heat. Reduce heat to medium-low and cook, stirring occasionally, until thickened, 5-6 minutes. Remove from heat and set aside.
Meanwhile, coarsely grate cheese.
1 (8 oz) block mozzarella cheese
Wash, dry, and, using a clean cutting board, shave cilantro leaves off the stems; discard stems and mince the leaves.
1 small bunch cilantro
When the veggies are done, carefully transfer them to the bowl used for the sauce and set aside.
Place pitas on the baking sheet. Return to oven and toast for 5 minutes.
4 whole grain pitas
Top toasted pitas with saucy chicken, cheese, and veggies. Return pitas to the oven and bake until the cheese melts, 3-4 minutes.
To serve, divide pitas between plates, top with cilantro, and enjoy!