Cut the chicken breasts into bite-sized pieces.
In a small bowl, combine garlic powder, salt, pepper, oregano, and red pepper flakes.
Toss the chicken with the seasoning until evenly coated.
Heat olive oil in a large skillet over medium heat.
Cook the chicken for 12–15 minutes, stirring occasionally, until fully cooked and lightly browned.
Stir 2–3 tablespoons of spinach walnut pesto into the cooked chicken and simmer over low heat for 2 minutes.
Preheat the oven to 375°F (190°C).
Place the naan or flatbreads on a baking sheet.
Spread a thin, even layer of pesto across each flatbread.
Sprinkle mozzarella cheese evenly over the pesto.
Arrange sliced tomatoes on top.
Add the pesto-coated chicken evenly across each flatbread.
Sprinkle with grated Parmesan and red pepper flakes if desired.
Bake for 10 minutes, or until the cheese is melted, bubbly, and lightly golden.
Remove from the oven and let the Chicken Pesto Flatbread cool for 2 minutes before slicing and serving.