Place the oven rack in the top position and preheat the broiler to high.
In a bowl, toss the chicken tenderloins with the yogurt and 1/2 teaspoon of the garam masala until evenly coated.
Line a baking sheet with foil and spray with cooking spray; arrange the chicken in a single layer, sprinkle with 1/4 teaspoon salt, and broil on the top rack 2–3 minutes per side until cooked through.
Meanwhile, heat the olive oil in a nonstick skillet over medium-high heat and add the sliced squash; sauté 2 minutes.
Add the remaining 1 1/2 teaspoons garam masala, grated ginger, ground red pepper, ground coriander, and minced garlic to the skillet and cook 1 minute until fragrant.
Stir in the drained diced tomatoes, simmer about 4 minutes until most liquid has evaporated, then stir in 2 tablespoons cream and 1/2 teaspoon salt and cook 1 more minute.
Cut the broiled chicken into bite-size pieces and add to the skillet; toss to coat the chicken in the sauce.
Place the naan on a baking sheet and broil 1 minute per side to warm and lightly toast.
Divide the chicken mixture evenly over the naan, top with sliced mozzarella and red onion, then broil 2 minutes until the cheese melts.
Sprinkle with fresh cilantro leaves and serve immediately.