Combine the yogurt, lemon, oil, garlic, ginger, paprika, cumin, garam masala, and cayenne pepper in a food processor. Process until smooth to make the marinade. Sprinkle the chicken thighs with salt and place in a freezer bag with half of the marinade, turning to coat well. Reserve the remaining half of the marinade in a separate container. Refrigerate 2 hours or overnight.
Preheat the grill to medium-high. Grill the chicken 5 minutes per side, or until it reaches 160 degrees F. Remove from heat and cut into chunks.
Brush the naan with oil. Mix the previously reserved marinade mixture with 2 tablespoons of tomato paste. Add additional yogurt to thin, if necessary, to give a spreadable consistency. Spread the naan with the tomato-yogurt mixture. Top with the red onion, chicken, mango, and mozzarella. Turn down the heat on the grill and place the naan pizzas on, or put the naan pizzas on a shelf above the grill grate. Close the lid and grill until the cheese melts. Remove from heat
Top the pizzas with mint leaves and cilantro, drizzle with yogurt, and serve.